So you have to do Motion/sM before any fire. This is because those DRM could affect your shot. The thing to remember about an sM is it can shoot SMOKE up to three hexes away. If the enemy AFV has Stopped and cannot move any more, Motion may not be your best option. He is shooting +2 Case B, +2/+3 Case C, and +3 shooting out of a SMOKE Location. He needs an Original 2 TH depending on Point Blank, BU/CE, target size modifiers. Your shot is only +2 SMOKE, +2 Case J and then the rest (possibly Case A when you placed SMOKE, BU, etc). When your PFPh comes, you will have a -1 acq (at least) and the chance to shoot IF. The SMOKE will also disappear. So if you have a reasonable chance TK (say > 60%), you stand to kill the enemy AFV more often than you lose yours.
For example, say you hit on a 7 and kill on a 7. We are going to call a SHOCK a mission kill for this because I don't want to do the math. If your TH# is an Original 7 and your TK# is an Original 7, you Eliminate the enemy tank 33% of the time (.58 * .58). If you don't get the enemy on the first shot, your second shot (still needing 7 for this example), you would still have a 33% of killing the enemy AFV. Taken in total, that's a 55% (.33 + (.58 * .67) of Eliminating the enemy AFV on two shots. If you get ROF in there, it goes even higher.
I have an article in J15 that touches on this. The gist: take the first best shot.
-- jim