I used a backpack for a little while, but it would always ride up my back and somehow get tangled with my helmet so when I moved my head, it would be snug. I hated it. I now use a Timbuck2 and I love it. If you get the right length for the shoulder strap and tighten the chest strap well enough, it shouldn't move. The flap has clips on it so I tighten them down tight too, and nothing will get out. There is an internal organizer pocket as well, so valuables can go in there. I can't imagine using anything else.