They are all good brands, but which one you get depends on which one feels right to you. The geometry will be different between the brands, and between different models in the same brand. IMHO getting the right bike size and geometry to fit you and your intended riding style (touring, commuting, road, mountain, etc) is the most important factor in buying a bike.

Since you've stated you want Shimano componentry the number of parts that you'll have to worry about as proprietary or hard to get are limited, so I wouldn't worry too much about that. Just pick the bike that feels the best to you when you ride it.