The diagonal-abusive DMs and circle motions are my biggest issues here.
I wish PPP/KKK were the only ones. At least an N-key rollover or 6-key rollover keyboard can fix this (as far as you said before).
The buffering went up only in the PC ports (SF4, KOF98UM, KOF2002UM) indeed.
Unfortunately, no emulator will ever be able to raise the buffers, since they have to be programmed into the game itself. The only thing emulators can do is making all of the DMs have easier commands by means of cheats (there are MAME and FBA cheat files who are able to do this in some games).
@Darksakul and @Moonchilde, why do you deem my observations about command buffering LOL-worthy?
I've experienced it myself: The smaller the buffer is, the quicker you have to input a motion for it to work. Older games with only one speed and diagonal-abusive DMs, like Global Champion/Kaiser Knuckle/Dan-Ku-Ga and the Fatal Fury series (after the first one) have a very small buffer and games who offer more than one speed suffer from this as well: The faster the speed, the quicker you have to input the motions.
If that wasn't true, Raging Storm wouldn't be easier to execute in KOF98UM and KOF2002UM and the 1-star speed in CvS2 wouldn't be the best to do Guile and Claw's diagonal-abusive DMs and even QCF-HCB DMs, for example.
You're possibly thinking that anyone who's into fighting games should know that, but I find it strange that neither you two nor anyone else in this thread did mention it.
Even @FreedomGundam, who said that the type of keyboard doesn't matter in terms of ease of execution, didn't say that what matters is the buffer the devs put into the motions during the making of the game.
I'm not mad at you, it's just for curiosity indeed. If I'm saying anything wrong, please correct me.
As noobish as this may be, by the time I opened this thread I hadn't yet discovered a thing called command buffer.
At least I finally found out what makes diagonal-abusive moves and circle motion moves harder to pull off in some games - or, depending on the game, speeds.
Such a shame, since it seems that the older the game, the harder these moves are to execute. Raging Storm, for example, has a considerably better buffer in KOF 98 Ultimate Match and KOF 2002 Unlimited Match than it has in KOF 96 and the Fatal Fury series.
I also presume that Capcom gave Rolling Izuna Drop a better buffer than Double Somersault's in SSF2T, since, at least according to my tests, it's way easier to pull off - at any speed - than Double Somersault.
Anyway, I've reached the conclusion that a gaming keyboard (mechanical or hybrid) would only be a good buy for fighting games if for better key durability and better feel when pressing the keys. How sad.