I think I can see a little bit of what your friends might be getting at with their comments.
If you get a flatnose bus, then you're sitting ahead of the front axle. Driving and steering from ahead of the front axle is different then driving a normal car or truck. It's nothing you won't get used to, but if you're on a narrow mountain road, it means you have to think a bit extra about where the wheels are vs. where the bus body (and you, the driver) are. You also have the stairs hanging down in the corner, ahead of the axle - which could impede the angle of attack. (This is a long one, but there are plenty of short ones just like it. Some of them actually have really short wheelbases, and can turn surprisingly well.)
Compared to a regular dognose bus, you've got the engine and the front axle ahead of you - better angle of attack, and you know (and can roughly see) where the axle is ahead of you. The stairs still hang down, but they're behind the front axle instead of in front of it.
How much of a mountain road are you talking about driving this on? No matter what you choose, it's still going to be big, and well...a bus. There are 4x4 options out there, but they can be harder to find, and they're not cheap. The only other thing I can think of is that the shorter buses tend to have some of the weaker transmissions, and I'm not sure they'd be as well-suited if you're going to spend a lot of time crawling up and down dirt roads.