I have two fuel belts that I have used for my long runs. One is better for training and one is better for racing. My sister bought me the FuelBelt for my birthday last year and I bought the Spibelt at the marathon expo last October. I haven't used either in awhile because I haven't gotten up to high double digit runs.
The FuelBelt has two 10oz bottles for liquids and a small pouch. When I first began running with it I was annoyed with how much it bounced. It took me a little while to figure out how to best wear it. I have a small waist so I had to strap it tight and push it down way low on my hips to get it to not bounce. I usually fill one bottle up with water and the other with gatorade. The pouch fits my house key, cell phone, and Gu chomps.
I like this belt for training more than for races because of how big it is compared to the Spibelt. I usually take the FuelBelt with me on 14 and over mile training runs. When I run shorter (13 and below) I only take Gu chomps with me. I did use this one for the 20 mile race I did last October and it worked great. I chose to use it to race only because it was along a trail and had few fuel stations.
The Spibelt is one small pouch that stretches out to fit a couple of Gu chomps or other fueling chomps.
Occasionally I have a race where they either don't have fuel stations or don't have a lot of fueling so depending on that I figure out which one will be best. For half marathons and shorter race distances I don't wear either.