Considering this applies to both Genesis and SNES versions (I think), I'm putting this here.
All my research was done based on the Genesis version, which I'm pretty sure is equally applicable to the SNES version.
Frame counts for basic movements:
Ducking, gun or no gun: 20 frames
Rolling, gun or no gun: 30 frames, 5 steps forward.
Standing out of a roll (no gun): 12 frames
Running: 24 frame startup + 10 frames per step + 40 frame slowdown (minimum 74 frames for 3 steps)
Walking: 4 frame startup + 24 frames/step
Standing jump: 78 frames, 4 steps
Turning around (no gun): 32 frames
Turning around (gun drawn): 24 frames
Turning around (Ducking, no gun): 20 frames
Turning around (Ducking, gun drawn): 22 frames
Turning around in "Ready to roll" position: 18 frames
Turning around in "Cautiously walking" position: 20 frames
Drawing gun (standing): 38 frames
Drawing gun (Ducking): 22 frames
Moving into "ready to roll" position (ducking, gun out): 14 frames.
Moving into "cautiously walking" position (standing, gun out): 34 frames
Taking a step in while "Cautiously walking": Roughly 30 frames/step
Note: All moves are reversible, i.e. drawing a gun takes the same amount of time as putting it away does.
Note: While ducking, a gun is drawn into the "cautious" position and needs to be leveled at an enemy. While standing, a gun is drawn pointed at the enemy.
Moving from point A to point B:
Lots of flat land: Roll repeatedly: Hold down as your roll ends, and you keep ducking as you come out of the roll. Release down and tap the direction you're facing to roll again. You move at roughly 5 steps every 30 frames doing this.
Short distances: Here I describe what to do if you're n steps away from where you need to be (switch, item, some guy, etc).
Standing -> Standing
1-2 steps: Walk
3 steps: Run
4 steps: Standing jump
5 steps: Duck, roll.
6 steps: Duck, roll, take a step
7 steps: Duck, roll, take 2 steps OR Run all 7 steps
8 steps: Run and immediately roll.
9 steps: Run, jump (except into walls, in which case run 4 steps and roll)
Ducking -> standing
1-4 steps; Stand, see "Standing -> standing"
5 steps: Roll.
6-7 steps: Roll, walk.
8 steps: Stand, run, roll.
9 steps: Roll, and during the roll hold up to do a standing jump immediately afterwards.
Standing -> ducking
1-4 steps: See "Standing -> Standing", duck
5 steps: duck, roll
6-7 steps: Take 1 or 2 steps, roll
8-9 steps: Run, roll.
Repeated rolling over long distances -> standing (distance from last roll possible before overshooting)
4 steps: Come out in a run, do a running jump (requires 14 steps).
3 steps: Come out in a run and roll once (requires 13 steps).
2 steps: Come out in a run and roll once, then come out in a running jump (requires 22 steps)
1 step: come out in a run and roll twice (requires 21 steps).
Note: Avoid starting out 1 or 2 + 5x steps short of your destination, especially if you're coming down a ledge or going up/down an elevator.
Moves during which you can change your gun-holding status without any lag whatsoever:
Rolling on flat land (draw or holster)
Rolling off a ledge (holster only, you must re-draw if you don't)
Jumping off a ledge (any kind of jump, draw only)
Dropping off a ledge far above your head (draw only)
Climbing up a ledge (Draw only)
Except when climbing up ledges, you'll end up ducking when your gun is out.
Dropping off ledges:
If you're rolling, shooting, or picking up an item immediately after you drop down, you'll want your gun out (it's faster). Otherwise, don't bother.
If you need to walk off a ledge with your gun drawn, it's faster to duck, draw, stand up and walk off than it is to draw it standing, move into the "cautious" position, and then fall.
Distance from underneath ledge: methods of doing so
0 steps: Climb down
1 step: Walk off
2 steps: Run or jump (running off requires you to start at least 1 step back from the edge)
3-7 steps: jump
Either kind of jump will put you an extra step past where you would normally land on flat ground.
You can turn around when you let go of the edge of a ledge by holding A and the direction opposite what you're facing.
Glitches:
Invincibility: You are invincible (i.e. won't get knocked down by bullets, mines, etc) if you are ducking, gun drawn and leveled, and turning around. This only really applies once in the game (As you'll likely pick up the force field after saving Ian from the many-HP policemen) but is an incredible life-saver nontheless. There may be a few other animations that render you invincible, too. However, you'll most likely spend most of your firefights as described: Ducking, gun drawn and leveled.
Walk through walls (confirmed Genesis version only): Stand right next to a wall, facing away from it. Hold A, tap away from the wall, then release A and hold the d-pad towards the wall as you're turning around. When you're done turning around, you'll be starting on running straight through the wall; at this point you'll probably want to hold A again so you don't suddenly start walking.