Those look like nice ultralight packs. The only issue I would have is the lack of pockets and maybe the durability of the material. I'd say you can use either one for all 3 purposes. They look a little big for hiking daypack but of course they're very light and you could cinch them down so they don't jostle about. I'm using an Osprey Statos 32 for a daypack and BOB. I've got my stuff a bit modularized so that when I go on dayhikes I can easily remove the BOB stuff I don't need to bring along. Its a little more work using your daypack as your BOB but for me its easier and cheaper than having 2 full seperate kits.