I've had both sold and hard covers. I currently have a BackFlip and it's hands-down the best cover I've ever had. They aren't cheap, but they are great. They mount between the rails, so you don't have anything sitting above like on most hard covers. I don't like the above-the-rim look, but I do like a hard cover. I also like the way you can just flip enough of it for what you're hauling to flip the entire thing for full-bed use. BakFlip Tonneau Cover - HOME
Had caps on everything before my last one which had a hard toneau. Lived with it but hated it. Always needed to haul something a little longer and a little taller than it allowed. Ecobeast has a cap which was order weekend after picking up the truck!
Kurly...also wanted to mention that you can get the Backflip in metal or fiberglass. I have the metal one, and haven't even seen the fiberglass version. I'm assuming the fiberglass version is a little lighter and probably doesn't retain heat as much as the steel. So you may find someone else that could offer more information on the fiberglass version of it. Again...I love mine and would never have anything else.