See with the puma, it does have more range, but AEC is general purpose and you don't give up healing going for AEC like you do going puma. If puma could fight infantry too I'd say it would be pretty OP considering it has 50 range and smoke.
You don't give up anything going puma, you simply get healing bit later.
However, brits do give up bofors for choosing AEC as well as they slow their tech down, whilst OKW just techs further.
Pumas main cannon isn't really AI beast, but its coax have the strength of LMG42, its vet1 ability extremely easily picks out brit sniper and retreating units with last man.
AEC fights infantry better, Puma fights armor better.