I agree that the TME rolled handles stay put a lot better than the braided handles. But they are such lovely details that I often try to make do by lying one on top of the other, or I just go for an extra strap option like a single shoulder strap on the Love Me or the messenger on the IB.
I also think the shoulder strap on the WTM (either size) is very comfortable. This is actually my favorite style because the shoulder drop is perfect for me and the slim profile of the bag keeps it perfectly in line with my shoulder so that it doesn't slip off and is very comfy.
#1 TME and a close second MMS. I also like my Tote Me - those straps stay on well too -- have a London Tote on the way so am hoping I love that too as I'm planning on carrying it a lot with my laptop in it!