No, they're not all the same, biohazard is more natural, you choose a weapon, go and find shelter, pray to god that no infected player followed your path, I guess the same goes with zombie plague BUT in plague you have more customizing ability to choose from, like lasers for an example (you can buy infection bombs as a zombie and antidote as a human etc..) there's a lot of more customizing to do there while in biohazard it's just natural, simple and more fun in my opinion, choose a weapon, go and find a good place to stay and try to survive while in plague you can you set up lasers in your location and buy a lot more stuff in the menu.
Does this make it easier for understanding maybe? Not all zombie maps fits biohazard style, they want it short, intense, simple and fun maps.
Zombie Plague can have bigger maps since zombies can jump like 10 miles from location to another I guess lol.