Good for you on getting some. They are lighter than the equivalent cam, so long routes you'll often do better. Furthermore, many areas take hexes real well, often better than cams. I followed a kid who did a ground up FA today and he used some. The larger sizes tend to do the best, as was said by others.

As far as which ones to get, they're all good. I think that climbing mag rated the Metolius and WC a tick better than the Black Diamond. The BD/Chouinards are very good though. I'd look to pick some up on Ebay cheap. If they have old cord, you can just retie new stuff. I still carry some hexes on occasion which I bought over 30 years ago, they don't go bad.

It's true that cams are generally easier to place, but there are times where falling on a hex is much safer. (camming a loose flake or block as an example, or where a classic bottleneck fits a hex but the flare in the back would cause a cam to walk with the slightest nudge.