Fixed gear on the road, of course.
MTB requires standing more as well.
Road really requires very little standing. I think many have gears too high and stand too often and/or too long when riding road bikes. Comfort out of the saddle is something that would never occur to me apart from a thread like this. The only thing I'm thinking about when I stand is how quickly I can sit back down.
Fit is fit and comfort is comfort. If your bike doesn't fit out of the saddle then your bike doesn't fit in the saddle either.
-Tim-