Same penetration so P4 does not have more AT unless you are speakin of long range combat Kappa but I never have that problem since I always rush my shermans in close range.
even with the same pen at close range, the pziv still have more armor.
2 radio net Shermans and a Jackson is a really potent armor combination. Shermans don't need to scale well individually because their meant to be used in groups with radio net, and to wipe squads on the flanks. Other than his abilities, the Major tier is the only tier I'm really happy with in the USF arsenal.
radio net is a vet 1 ability that only affect that particular sherman. the blitz is just as good if not better.
btw, the sherman and jackson vet1 cost more than the vet1 on the pziv.