OMG I'm so glad you brought up this topic! I was actually just posting in a thread in Melee discussion (
HERE) which was a new player trying to decide between playing Marth and Falco. The thread has most of what you hear these days: suggestions telling people to pick one character and stick with it. While I obviously understand the benefits of dedicating yourself to one character, I've always felt it is a highly overrated way of learning to play, ESPECIALLY for new players. My post:
Essentially, I feel like most elements of gameplay in Melee can be divided between general skill and character specific skill. How you approach, combo, recover, etc. are all character specific elements, but there is always overlap between character specific and general. General skill would simply be ideas, tactics, or methods that apply to multiple characters. It probably sounds pretty abstract, so I'll just use the example of approaching since that's what PP mentioned.
When you approach as Falco, obviously you have many Falco-specific things to consider when building a style of approach. You have lasers, a pretty short dash dance, a slow dash, and each aerial with a different hitbox that covers different areas. Obviously there are more elements that come into play, but these are the main ones. While these traits influence how a Falco player must approach, there are also many similarities to most or even all the other characters. All characters can dash dance, but some can dash dance better than others. A lot of characters have projectiles, but some are much more useful for approaching than others. You get the idea.
When you build up your entire knowledge of the game around a single character, it's very possible for you to unknowingly gimp elements of your gameplay because they are less important (although not useless) for your character. A simple example of this is a Sheik player. If a new player picks Sheik and doesn't really try out anyone else, they will definitely get good with Sheik, but it is reasonable to assume their dash dance game will be much worse than a Falcon player who relies on dash dance frequently. Without very limited knowledge of dash dancing, a Sheik player could quite easily become a decent player. Similarly, a Falcon who doesn't rely on WDing for spacing like the Sheik player could also do just fine. However, it seems to me that once you reach a certain skill level, these small tidbits of knowledge start to build up and you begin to realize you are missing a fairly large chunks of tactics to utilize. Sheik players may not usually dash dance, but I'll tell you what, I've definitely seen M2K's Sheik do some insane dash dancing to pull off things that otherwise could not have been done. I've also seen many top Falcon's display how dominant his WD and waveland can be, but only when being utilized with near perfection.
My theory, as you can probably see, is that in order to build a solid foundation for your overall gameplay, it is important to learn as many techniques as possible in order to expand your potential for your main. Even if a technique can only be used in a scenario that shows up in 1/500 games, Melee seems to have reached the point where those kinds of game knowledge can make or break you. Any time I see top players TRULY improvising in game, I can't help but think it is largely in part to their vast experience with a lot of the game from the perspective of many characters, not just one. Even things like Mango's Marth being extremely aggressive are examples of this. Mango's tendency to be aggressive is clearly a trait of himself as a player, not merely the beneficial strategy for his main. In all of his characters from his Mario and Link to Fox and Falco, you can see a very unique spark of aggression that makes his style his own, and also makes it work. I believe that is the sign of a player who truly understands the game and has not simply learned to analyze situations based on matchup-specific ideas. If you know what Falco could do to edgeguard Fox, that is great, but knowing what EVERY character could do in the same situation may help you realize Falco has a lot more options than you thought.
Essentially, what I would recommend to anyone starting out, even though I'm sure it's controversial, is to play all of the characters until you have at least a decent amount of comfort with all of them. You don't have to know the matchups inside and out for each character, but simply learning the different tools available in the game can help prepare your main to deal with situations with as many tools of his own as possible. Obviously this way of starting out has some definite cons to it. Someone trying to learn the gist of all the characters is going to progress a lot more slowly, and it may definitely be a lot more frustrating and difficult. However, I feel this pays out in the end as I've seen many mid-level players (mid-level being the players who tend to be seeded around the middle of their region; i.e. Me) who aren't bad, but seem to have many character-specific crutches they rely on. A Falcon who spams dash dance can get a lot of grabs on many low-mid level players, but once you get to that mid level you seem to hit a brick wall and all of the crutches and traps you've set up with your character begin to stop working on the experienced players who've seen it all. Falcons can no longer rely solely on their dash dance to get grabs the same way Marth players can't rely on players missing L-cancels to get shield grabs. Had these players used multiple characters, they might not have learned to play the game by relying on these character-specific tactics, and they would be much more capable of using general skill to out-space, out-punish, out-recover, etc. against good opponents.
I'm not just throwing out pure theory here, either. I would definitely consider myself a player who can play well with many characters, and I make a conscious effort every time I play to try multiple characters and see what I can come up with in terms of tactics to deal with different situations. I typically only get to play DJ, a pure Marth main (as in, only Marth), and I actually played him last night. He uses spacies a couple games, but not nearly as talented or as serious as his Marth. In the time we played, I played at least
several games with all of these characters: Falco, Fox, Marth, Ness, Mario, Doc, Falcon, Ice Climbers, Jigglypuff, and Sheik. I have a feeling many people view me as someone who isn't too serious on improving because I actively practice so many characters, but I have definitely noticed major improvement in my Falco game due to all of my other characters. Simple gameplay elements off the top of my head that I have taken from other characters and implemented into my Falco:
Marth - reacting to get-up-attacks/rolls rather than predicting; WDing out of shield with fsmashes; tomahawk grabs; fox-trotting to avoid approaches; powershielding approaches/lasers
Fox - edgeguarding with a combination of ledgehog, shine, and bair; abusing is epic ledgedash (shoutouts to Wenbo!); approaching with dash cancelled shines; uthrow punishes; using platforms for approaches more
Ness - shield pressure by hitting their shield then moving slightly out of their range to bait something (from Ness being able to abuse DJC bair, dash away, repeat); different areas to aim the Firebird at, like sweet spotting vs. slightly above the ledge (Patches O'Houlihan: "If you can recover as Ness, you can recover as anybody." lol)
Mario/Doc - REALLY helped improved my jab game; wavelanding onto plats for regrabs/dsmash punishes instead of just shine-wavelanding all the time (shoutouts to Boss!)
Falcon - if you have a bad spot dodge habit, pick this character!; has also helped me utilize double jump punishes b/c I spam double jump stomp a lot lol; being more patient in general when dash dancing; having the self control to not jump off the stage (still working on this one...)
Jigglypuff - Spacing with this character is so hard... (shoutouts to Mahone for playing 99% Jiggs against my Falco my entire first semester of competitive Melee... uthrow rest wut iz dis BS?!) I feel like a scrub because I can do insane tech **** with Fox/Falco, but I frequently miss L-cancels that have those awkward timing being you started the aerial at the top of a full hop, but can't L-cancel until a lot later. lol I started using her WD much better yesterday, so that was an improvement. I still want to try out Hbox's patented full hop nair fade away **** that I've been seeing him do like mad somewhat recently.
Ice Climbers - I picked up Ice Climbers after rooming with Chu for Zenith (shoutouts to Alex Strife!) and getting my mind read 24/7 in about 300 friendlies. lol I'm learning the general types of attacks that tend to lead successfully into grabs, and with Sopo specifically, I have improved a lot more on reading opponents after throws. Chu just boggled my mind with how well he can hard-read opponents with Sopo throws. He will back throw you, and then it just seems like he covers 10 options without even moving or with a single attack. I think this will help my throw game mostly vs. Fox for stuff like dthrow/bthrow mixups where he doesn't fall over and it tends to come down to being able to read whether or not they are going to spot dodge, roll, or shield.
Sheik - This is my most recent addition to my cast of characters. I am hoping to greatly increase my ability to utilize WDing as a spacing tool. I identified it as a pretty weak spot in my spacing game a while ago (I tend to rely heavily on retreating lasers, a
character specific tool, mind you) and I am confident that playing her will improve my ability to recognize situations where a WD approach/retreat is more beneficial than a dash or jump.
Peach - I can't float cancel. This character is too hard. D: (Shoutouts to Armada for
rubbing it in my face!)
tldr; Wow, I typed all that and you won't even read it? Jerk...
Minor disclaimer: I am in no way trying to imply that playing multiple characters is the only way to get good. It's entirely possible someone could play one character all the time and still be able to see the options other characters have and apply them, but I just think it's much easier to comprehend and develop the other options when you have experience with those characters beyond spectating.