I've got those Elite ones in the piccy above and like them. Resistance-wise they're comparable with riding on the flat (I use them with an MTB with slicks on), but it's not variable. I was told to get a set with the biggest drums I could find, apparently it makes them roll better (which makes sense), and the Elites have the biggest. The "parabolic" stuff is just marketing BS IMHO, they're flat except at the edges and if you're riding out there you'll fall off regardless!
It's hot work without a fan blowing some wind in yer face, and boring without a telly or hi-fi