I think the OP has Panzergrenadier and Grenadier mixed up.
Panzergrenadiere will win if they are unupgraded. If they are upgraded, I'd expect upgraded guards to win but it'll be a random clusterfuck anyways because nearly all men will just be jumping around.
vs. upgraded Grenadiere I'm really not sure. The DP LMG and the LMG42 are both pretty powerful but the LMG42 is pretty prone to being useless when the Grenadiere try diving for cover. The anti tank rifles of the guards will thus mess up the Grenadier AI, preventing them from firing a lot.
You can also look up
Adder's DPS chart and estimate their performance from there. However, the anti tank rifles will kill with one hit but not hit very often thus making the whole thing even more random. Overall, I think the more expensive guards would win.
Don't have too much experience here on the other hand. It is an engagement that is very unlikely to happen in a vacuum.