I'm for different powers for each zombie type. Possibly something that counteracts there weakness's or helps there strength's more. ex
(/=or)
Classic: Takes less damage/more durable
Predator:Goes completely invisible for short duration 2-3 seconds/ Higher jump radius
Speed: Less knock back for a short duration 3-5 seconds/ More hp
Deformed: Speed boost for short duration 2-5 seconds/Burn damage doesn't affect for short duration 5-10 seconds
Tons of other suggestions prob better than these but all i could come up with on the spot. Believe it would help make things unique because there would be diff powers for each class.
It's only my opinion, to each their own.