I am a rack and panniers guy when loading the bike significantly, as in a multi-day tour. When more lightly loaded, I like a medium to large size waist pack. It is low to the ground, doesn't affect my agility on the bike as far as I can tell, and stuff in it is always with me. That stuff will usually include a Wave, although dedicated bike stuff (patch kit, hex wrenches) is typically stashed in a bag hanging from the saddle.