Rotor make adapters that fit pretty much any of their cranks onto any frame, budget and the degree to which you are a weight weenie will probably be the largest considerations if you need not worry about swapping between bikes and potentially having different adapters on each bike.
As for me having 2 bikes with BB30 bottom bracket shells, yes, you are correct, both of my geared bikes have a BB30 bottom bracket, so I would choose a BB30 crankset so I can swap it around easily. Rather than buying 2 expensive cranksets (if loaded) or 2 cheap cranksets (if budget limited), I would buy 1 of the best I could afford and swap it (best performance for least cash). This is what I do with my power meter because I definitely can not afford 2 of those.