Different from SF2, the 4 kinds in 3rd Strike seems purely visual. 
They are character specific as the following:
Birds - Ryu, Akuma, Ken, Hugo, Chun, Ibuki, Elena, Makoto, Necro
Stars - Q, Yang, Dudley, Sean
Reapers - Remy, Urien, 12
Angels - Oro, Alex
The time upon which you last stunned seems to be a random between 4 numbers, depending on what was the last hit that stunned you
Normal - 90 or 110 or 130 or 150 frames
Throw - 120 or 140 or 160 or 180 frames
Special - 150 or 170 or 190 or 210 frames
Special Throw - 120 or 160 or 200 or 240 frames
Super - 120 or 160 or 200 or 240 frames
Super Throw - 150 or 190 or 230 or 270 frames
Each directional and button input decreases in a frame the rime of recovery, hence, mash it out
As an additional info, stun bar lenghts:
Gill - 72 pts, recovering 1 every 20 frames
Hugo - 72 pts, recovering 1 every 21 frames
Dudley - 72 pts, recovering 1 every 22 frames
Q - 72 pts, recovering 1 every 22 frames
Alex - 72 pts, recovering 1 every 23 frames
Oro - 72 pts, recovering 1 every 24 frames
Makoto - 64 pts, recovering 1 every 20 frames
Urien - 64 pts, recovering 1 every 21 frames
Chun Li - pts, recovering 1 every 22 frames
Ryu - 64 pts, recovering 1 every 22 frames
Ken - 64 pts, recovering 1 every 22 frames
Elena - 64 pts, recovering 1 every 22 frames
Sean - 64 pts, recovering 1 every 23 frames
Necro - 64 pts, recovering 1 every 23 frames
Twelve - 64 pts, recovering 1 every 23 frames
Ibuki - 64 pts, recovering 1 every 24 frames
Yun - 64 pts, recovering 1 every 24 frames
Yang - 64 pts, recovering 1 every 24 frames
Remy - 56 pts, recovering 1 every 21 frames
Akuma - 56 pts, recovering 1 every 23 frames
Anyways, much love to the thread! Iâm switching to Remy, so Iâm soaking up on the infos here :]