I'd go with O. Folks are correct that some of the doorways will be too tall, but if you're dealing with minis on bases (especially 3mm slottas), they look quite natural. The compressed footprint of most O "scale" buildings will look just fine.
Also, when dealing with O trains, the pricey, truely 1/48 scale trains are pretty huge looking. However, alot of the 0 gauge trains (especially the starter sets intended for 0-27 layouts) are quite undersized. As well as being more affordable, they tend to be very close to 28mm scale.