Hi. I just went to LV in Mclean, VA, tried on many bags, including Bloomsbury PM and GM. I was looking for a messenger-style bag larger than the Biosphore (which I have carried for the last few yrs when doing casual things and running errands), with some depth, but not so thick and wide.
The Bloomsbury PM, although of similar depth as the Biosphore, is more accommodating -- i.e. I can put Blackberry, mobile phone, 2 wallets, checkbook, keys AND compact, without the bag looking bulgy. The width and height of the bag make it more versatile than the Biosphore. And it doesn't turn color like the regular monogram version of the Odeon or the Biosphore.
The Bloomsbury GM, which I also tried, was too big for my body frame (5ft3in). The GM size was WIDER than my body from the side view. It looked like I was carrying a super large reporter bag.
Last but not least, the Bloomsbury has zipper closure; very important for someone who flies a lot. I don't want things to fall out while the bag is passing through x-ray security check. Also the PM size is small enough to be taken onto the plane and placed in the backpocket of the seat in front of me (in case I run out of space to put luggage on the plane).