I have 3 different bags that I use for commuting, some in combination: a Carradice Barley, Acorn Med-Large seatbag, and a Rivendell front rack bag. The Barley holds the most gear and I use it most often, and the Acorn is perfect for days when I don't need to carry any extra clothes. The Rivendell bag is only used when I have an extra large amount of gear; I don't like the way it affects bike handling, particularly on windy days, so it doesn't get used a lot. I am considering getting a second Carradice bag, the Pendle, which has 50% more volume than the Barley for days when I need to carry more gear.