I own both the LARGE Downtown and the OVERSIZE Muse, and the Downtown is actually a bit bigger. Both of them hold a ton, though. I use them for work and have room to spare, lol!
^The large downtown is big . Even the medium that I have is roomy, like my OS muse. The RG is big, too like Alice mentioned above. You should try all 3 and let us know what you got!