See how you just did chicken in the egg there...
Once guards are seen THEN the lmgs tend to come out. And now you have no counters. Just like the flameht comes out after the shocks hit the field. So your prior arguement is only valid if i have acess to bith sts and guards. Me i like to remove shrek squads more than crappy ass button so i tend ro go sts.
If he is floating munitions then you don't need elite troops because you can beat him with vanilla units. Continue to execute your strategy without selecting if you wish. My point is only that if you see lots of lmg grens (which by the way guards can easily win against, just pretend to throw a grenade and grens have to keep moving, lmg = useless) then go shocks. If you see 1 lmg gren squad, then that is no real threat. Just make sure you are in cover when you engage it and force it off the field first by targeting with as many units as possible.
If you consistently struggle against inf choose shocks, if you need to quickly destroy light vehicles choose guards. If you plan on using lots of T34's I would also choose guards.
You don't understand how good guards are so you attack me. I can tell you from experience, if you learn to use the unit fully it will not disappoint you.
I also want to make clear, yes button is 40 munitions per use (in a munitions light faction), but unlike shreks for the Soviet the Ost player never knows when you are going to do it. Therefore, you can drop it whenever you fine it most helpful and at critical moments in battle. The shreks are obvious once you see them you know he is going after your tanks. Guards are a thinking man's unit, and the ability to stop a tank for 40 munitions and allow you to get 1 or 2 more shots off is killer. It also requires the tank to accelerate from a stop, making it slow even after.
Everyone agrees Soviets float munitions but as soon as someone says "You gotta keep using them to stop tanks dead", everybody else goes "Oh I don't have the munitions for that". Seriously, you have the munitions, you are playing Soviet.