Zoo is the most visually interesting, but it's the most cluttered. Still, other than that monorail in the back and the mountain in the middle, there's not a lot of campy spots, it's mostly all on ground level, and it's not wide open like array. I wouldn't really call it a sniper map, since those high spots don't overlook much of anything.
I like convoy because it has a clear, symmetric theme to it. You can get into some really fun fights across those overpasses, but there's plenty of opportunity to flank.
Stockpile is my least favorite, with that building in the middle. It reminds me of that CS map where you can get in through the garage or the vent, but inevitably the first one through gets shot from a random direction. it just seems too chaotic in there.
Hotel is fun - the inside of the hotels are great for close quarters battles, but opens up a little in the middle. Great domination matches.
The one thing they have in common is that they're all large, sprawling maps, with twists and turns everywhere, like most of the BO maps. You would think nuketowns popularity would give them a hint that a lot of people dig the small, symmetric little arenas. Unfortunately, none of that here.