I like the roll ups, you get total bed access and no rear view blind spots
Extang Revolution. Had that on my last truck, was the nicest roll up I've used. Low profile. No snaps or velcro and still weather resistant. When fully rolled, its pretty small and it sits mostly on top of the rear bed rail so there is very little to no lost bed space.
I'm kinda torn if I should get it again or try something new just for fun. I really like the retractables, but I worry about losing a foot of bed space on a 5.5 ft bed. Some of the hard folding models out there look nice closed, but I hate having them block the window when up. If I went this route, I'd want one that I could pull off quickly and easily when needed.