The following is the summary of a conversation I had with myself today (uncertainty added for dramatic effect, the opinions expressed in this reenactment are mine and have yet to be validated) ...
I was trying to explore the option of ftilt vs dtilt in certain situations today; particularly in the neutral positions and was wondering why dtilt was pretty much always the better option than ftilt. Basically, I was trying to figure out why dtilt is herald as some god-technique in pretty much every MU but ftilt is hardly ever mentioned. I believe the question came to me when I was viewing an old thread by Ether where he was asking for some tips regarding Marth dittos.
Now from what I've seen, every strategic theory of the ditto suggests that dtilt is an amazing tool in the match. And I can certainly see why; it's (pretty much) perfectly safe if done correctly and at times is really your only approach method... or is it?? However, I couldn't figure out why it was valued so heavily over ftilt. After all they both come out on the same frame so speed isn't an issue (unless I'm missing something obvious), they both seem to do relatively the same thing: keeping your opponent away or providing a safe approach, and both take advantage of Marth's ridiculous range.
Obviously, I'm no frame/hitbox guru but I think a tippered Ftilt provides more knock-back than a dtilt. "Ah ha!" I thought to myself maybe the purpose of those moves isn't so much to "keep the enemy at bay" as it is to create an opening; after all there has to be a reason that dtilt is revered as much as it is and why poor ftilt is hardly ever mentioned. Basically, a sweetspot ftilt would knock your enemy further back but it would keep them out of your threat range. I may be wrong but it's probably a bad thing. However, sourspot ftilt could easily keep the enemy close and within your threat range. So maybe I was missing something.
I mean both attacks seem to pay homage to the old zoning "put a hitbox out there" strategy that most Marths employed back in the day but if the metagame is asking for us to move away from that style of play into one centralized around superior movement, dashdance camping, pivots and other things that abuse Marth's superior range/priority. And of course when thinking about it more extensively dtilt fits into the puzzle quite nicely... but I don't see how ftilt doesn't.
Still there had to be a reason that so many of you mention dtilt in nearly every strategic discussion of Marth's neutral game but nary a mention of poor neglected ftilt; so it was back to the drawing board. Then I started to think about how the trajectory of the moves would be beneficial or detrimental to Marth's overall gameplay and decided to return to my thoughts on the differences in knockback. Ftilt's hit trajectory (whether sweetspotted or sourspotted... or bitterspotted, or saltyspotted) offers no real reward and actually resets the match back to the neutral game; so really all of your hard work, meticulous calculations and micro-adjustments you've made in the neutral game just got thrown out the window. Essentially ftilt did nothing for you. Dtilt on the other hand keeps the enemy close, you're still a threat to them ,can easily be followed up by any number of things (like a grab, cause yay grabs) and accentuates Marth's overall gameplan. While ftilt just shoos them away really. So that's the reason why dtilt beats ftilt in the neutral game pretty much all of the time.
I'm not really sure why I bothered to type all of that out, but the Marth boards were being too quiet. Feel free to add or disagree with anything that I've mentioned of course.
Thanks for reading!