Both and then some. For big load days I go panniers. For small or medium loads I go trunk with drop down panniers. Depending on the destination or any planned stops where I might want to just carry one bag in the store or something, I've got a large handle bar bag that I use as a pannier more often than I mount it to the handle bars. It's easier to carry around somewhere then a set of panniers or my trunk bag. If I know I'm going to be off the bike with a medium to large load, I've got a Nashbar backpack than can convert to a pannier.