There could be a few mistakes here, so take look at it with some skepticism. You should hard refresh if they don't start jumping at the same time for you (Ctrl+F5).
---------------------------------------- Brawl ------------------------------------------------------------------------------ Smash 4 ------------------------------------------------------------------------------- Project M ---------------------------------------------------------------------------- Melee -----------------------------
Total frames (brackets indicate amount of frames right before landing animation):
Brawl = 53 (50)
Smash 4 = 45 (43)
Project M = 39 (37)
Melee = 39 (37)
Frame that second jump starts:
Brawl = 16
Smash 4 = 16
Project M = 15
Melee = 13
Another thing to note. They all start falling at the 23rd/24th frame (Melee seems more like 22nd/23rd frame).
All 0.03 seconds per frame (30ms/frame)
It isn't a different GIF, but I still feel the PM one is missing a frame.
This measures fall speed assuming the jump heights are the same. And it clearly isn't, but still interesting to see.