Here's a summary of both Pokemon
Ampharos
Pros
-Very bulky
-Nice coverage
-Good special attacker
Cons
-Very slow
Pawmot
Pros
-Great psychical attacker
-Very fast
-Nice coverage
Cons
-Its frail
-It takes longer to evolve
-Dosen't get that many psychical Electric type moves through level up
I personally would go for Pawmot because you get it right at the start of your journey and Electric/Fighting is a really good type.
Hopefully, this helps :)