That Olimar aerial frame data is pretty mediocre; they're not "slow", but they're sure not "fast" either. Snake's bair and dair are actually fast to come out which is my bad for not recognizing that, but all three of the others are sluggish (10f for a uair and a nair, usually fast aerials on other characters, is fairly poor) and the point stands that they take forever to resolve to the point that if Snake doesn't hit he's basically completely free to a punish with them.
I'd also like to reference this oldie but goodie:
http://smashboards.com/threads/internal-character-mechanics-values.244329/
First of all to finish the previous point about air games, both Snake and Olimar have awful aerial mobility ("awful" is probably too kind of a word for Snake's aerial mobility...). Mobility is just as important as aerials for a good air game, and they lack. I mean, I'm not goin to deny that overall both are excellent characters; they're just excellent characters who are weak in certain important areas which is the formula I believe we're going to see with smash 4 characters in general. If not for Meta Knight, Brawl would have already been the first test case really.
The bigger reason I bring up that thread is the weight stuff. In terms of weight out of 39 characters, Marth ranks 27th in Brawl while Zelda and Sheik are tied for 28th. I don't see how both could be called anything but lightweights; they aren't as light as Jigglypuff, but they're still significantly lighter than a typical character. I would not be surprised at all to see Rosalina in this weight range, and it wouldn't contradict anything we've been told. Zero Suit Samus is the lightest full sized human in Brawl, and at rank 32/39, I think that's about the floor for how light a character of that size is ever going to be in a smash game.
In terms of resistance to vertical KOs, it does have some effect, but I recall it being pretty small. I decided to do some in-game testing on this point to see what the numbers say...
Mario's uncharged no DI training mode usmash lowest integer kill percent on Final Destination (weight in parenthesis):
Samus (108): 128%
Captain Falcon (104): 136%
Bowser (120): 137%
Falco (82): 116%
Olimar (82): 114%
This tells us a few things. Both weight and fall speed are factors in your overall vertical KO resistance. Weight is the dominant factor and determines the general neighborhood you're in, and if you're a lightweight, fall speed has pretty little impact (Falco falls so much faster than Olimar, and it's only a 2% difference even from Mario's fairly weak usmash). On the other hand, if you're heavy anyway, fall speed can play a bigger role; Samus is still harder than most characters to kill off the top, but she doesn't get the same kind of protection that heavy and fast falling Captain Falcon has, protection so strong it is barely worse than what Bowser has! This kinda does prove the point I was making that Rosalina won't be especially scared of vertical KOs since she's a lightweight and with Brawl mechanics she's going to be about as well off as any other lightweight, but this also does prove that I left out a significant part of the story for which I do sincerely apologize (I really do hate spreading misinformation).
Well, that was fun; I haven't disagreed with someone on these boards and done in-game testing in years (I used to do it all the time!). Man, I sure look forward to smash 4 coming out so we can have these sorts of disagreements in earnest and then I can post walls of text mixed in with numbers from that game!
