Okay so Brawl's stricter tech timing was poor coding and really just an accident. The arguements for buffer thusly seem to be mostly comprised of a rather real possibilty of driving away brawl players who are very much aware of the global buffer's existence. (along with an attempted, but probably sarcastic counter-concession of returning the brawl tech-window.) But that was covered above and would only amount to 4 frames of difference, whereas the global buffer goes up to 10.
Melee having buffer frames is kind of a moot point as iirc they have already been carried over into the project and didn't impact the tech-skill requirements of the game at all. But to be fair maybe having global buffer wouldn't be a bad thing at all, perhaps more perfect players by default, even through a frame-crutch or handicap, would make for a better game. I'm not certain it would, but it IS possible. But what of the people who have worked hard, and are still working hard, on their tech skill in a 0-buffer environment? Should the people with the pre-existing aptitude have to adapt to playing those with assisted skill? Aluminum bats are not allowed in pro baseball, the guard rails don't go up in bowling tournaments, basketball games don't lower the basket for the underdog team, and you certainly dont get to hit into the doubles lines in singles tennis.
In essence buffer really is like giving someone that extra few feet to hit the ball into, it allows players to perform at a higher level of consistency and "skill" by giving them more leniency. It also allows them to perform shots, or in melee's case techs, that are more difficult and may even be impossible for someone without buffer. But since smash is a video game perhaps having a more equal playing field, somewhat independent of player tech-skill, would make things more interesting. I can't imagine the trick shots pro bowlers could do with rails up, and Federrer vs Nadal with double courts would be disgusting lol!
However I still feel the argument against buffer is far stronger. Melee is, after all, the game PM is trying to emulate, and Melee has a very high tech-skill requirement, plus a very low error tolerance. It also has a massive gap between true casual, semi-casual, and tournament-level play. A global buffer makes more difficult timings easier, if not making certain things possible in the first place, and ultimately would pretty much by definition not belong in a game trying to replicate one of the most technically demanding games in existence IMHO at least. Plus I think fox with 10 frames of buffer is just dumb, multi-shine to shield break via-spamming erry-day.