From memory I think Wehr shreks deal 120 damage and PE shreks deal 85 damage (compared to 70 for bazooka, or 30 for PTRD). All other stats between the shreks are the same except for some target table things against M8s only introduced in 2.602 I think. I can't be bothered to check though. PE offensive vet can increase the damage , accuracy and fire rate substantially though whereas Wehr shreks can't be built or picked up by any units that get offensive benefits from vet, only defensive.
The numbers ingame are completely meaningless. It's extremely annoying repeating that. I hate relic for putting those in.