Very good analysis. Personally I still prefer a PaK because of how much better it is against armor, and like Barton I find the barrage to be very underwhelming for 60 munitions. (Example - watch Barton barrage Hans' position in game 2 of the most recent SNF. Hans has like 4 squads in the area, loses 3 total models and walks back about 5 feet. Yeah, not worth the price). Ultimately I believe that ZiS/PaK comes down to personal preference for many reasons already stated in this thread.
However, I believe that when a squad re-crews a weapon, it keeps all properties of that squad? As in, if you recrewed a ZiS with Pgrens (not sure why you'd actually do this but... for the sake of discussion) I believe they'd keep their armor and guns. Unless I mis-heard PQ on the most recent SNF stream he was saying that re-crewing a HMG42 with Shocks will result in a 2.25 armor crew... with PPSH-41s... and the HMG. Yeah, have fun trying to kill that.
Anyone else have better clarification on this matter though? I'm not positive I heard PQ correctly, but I do think that re-crewing (not merging) keeps all properties of the squad that re-crews.
Yes, they retain all their stats. This includes reinforcement costs, so while the HMG squad will be tough to kill, it will also be very expensive for the soviet player to reinforce. Considering that support weapons can't move, using rifle grenades will cause a huge MP drain against a soviet player using shocks to re-crew support weapons.
Fun fact for soviets: If you have Penal troops, use these to re-crew weapons and use conscripts to merge with them instead of using regular reinforcing. It will cost less, and give you better weapons without weakening the squad with lower armored units.