I have a Kipling Sherpa (roughly 15" x 11" x 8") that seems to be just the right size and right amount of organization but as I'm getting older, I'm starting to find that it gets too heavy to carry for long distances once I put my laptop and electronics in it. Ideally it would also have padded backpack straps so I tend to default to a Ellington Juno convertible tote-pack which is a tiny bit smaller. Anything larger than these bags, I go Eagle Creek convertible Adventure Weekender or an IT wheeled carry-on with a lightweight purse or slim brief-tote just to redistribute the weight and have somewhere I can quickly and securely put my phone and wallet. The purse and brief-tote can still be stashed in my larger bag if needed.

I'm currently looking at the Tom Bihn Western Flyer as a compromise between my smaller bags and my larger bags but haven't pulled the trigger yet. The sweet spot seems to be in the 20-30L capacity range for me depending on the season and the type of trip I am taking. I suppose, if I jettisoned my mini travel tea kettle, teas and chocolates, I would be able to decrease the weight of my bag by at least 1 lb or more.

In the back of my closet are Patagonia MLC, LeSportsac Pullman, A.Saks 21" expandable carry-on and an original Eagle Creek Switchback convertible wheeled-backpack.