Depends on your your total volume needed for cargo. I really like most of the Nathan products.
It also depends on your comfort, it's an individual thing. I cannot stand anything around my waist, so I hold a water bottle with a pouch. I also use the Nathan products. Go to a local running specific store and they can walk you through all their products and have a face-to-face discussion on what might be best for you.
I also use Nathan products, like Jennifer said above, it depends on your comfort. I love my Nathan because it has a nice sized pouch for phone, ipod, keys etc. :) Good luck!
I ended getting a nathon that holds 2 waters... I love it! Thank you for all your help and advice....