I've been debating this for a very long time. I currently am so used to "flipping" open the lid of my Lowepro Nova bag but I've outgrown it.
The Lowepro Magnum is probably the next step up in this design. But, I am getting older and wonder if its time to go to a roller bag like the TT Airport Security.
I doubt that it makes a different what I'm packing since there will be "growth" factored in to either bag, but currently I have two bodies with attached lenses (5D3 w/24-105; 7D w/17-40) plus 70-200 f/2.8, 100mm macro, 50mm, 580 EX II, etc.
Neither of these two bags would be "day" bags but primarily used as a single place to store and transport all the gear.
Thoughts from current users of either or both would be much appreciated.
No such thing as a perfect bag - but I keep trying.