I think the main things are Vampires being able to sense inside buildings (with not having to enter buildings, this may as well be 50% or so extra AP for the purposes of finding prey).
Barricading can mitigate this, but it's a pretty big AP investment to basically be painting a big "I'm in here" sign on the building. Even if you were to build a barricade to try and trick vampires, you'd have to spend a minimum of 5 (6?) AP to get it to barricaded status to prevent prying eyes. They, however, would only have to spend a minimum of 1AP to look inside and see through your trick. Now forgive me if I'm mistaken, but I'm pretty sure vampire claws and fangs have low chances to break barricades, so I'm sorta sure that barricades were originally supposed to be like a vampires bane, whereas zombies would have less trouble getting through them. However, the sledgehammer makes absolutely short work of any barricade. And not only that but I'm also pretty sure vamps would have a higher to-hit chance because of zombies natural melee debuffs.
Barricades are a joke against vampires.
So that's point 1
Point 2 is that Zombies and Vampires never need leave their preferred forms. With cursed blood and cellular degeneration revival serum is not only meaningless as a weapon, but actually beneficial for zombies with whatever that skill is. I just think this is really stupid. I'm sure this is just a holdover from festering brainstem or whatever that skill from urban dead was, and it was just as stupid there.
Then there's just the smaller, slightly inconsequential details. Like the damage reduction for vampires. I had a level 1 guy doing 1 damage to me because of my kevlar vest and supernatural durability. That has got to suck for new players, especially when damage and xp is 1:1. Building barricades doesn't give XP, but breaking them does. Writing Graffiti doesn't give XP but defiling it does. Killing a vampire with the DoT of zombie infection doesn't zombify them.
There's probably more that I can't think of at the moment, and probably more things that humans need to be balanced with. And that's just balance, there's a few things that might make the game more playable.