I had a hard roller on my last truck, Truxedo Sentry CT, and really liked it. However, I went with a soft roller, Truxedo Pro X15 on my current TB for the following reasons: 1 - I did not need the extra security the hard roller provided (but it did offer much better security). 2 - I wanted to be able to close the tailgate without having to pop open the cover (wasn't a big issue with my last truck, but with the auto tailgate on the TB, I could see it being a annoyance). 3 - cost savings over the hard roller(for added security I didn't necessarily need).
The hard roller does look much cleaner with no flap on the highway, is much more secure, and rolls open and shut much more efficient as well, I just wish it didn't need to be popped open to close the tailgate. I have friends with the Bak Revolver and/or GM equivalent, which does allow for the tailgate to be shut in the latched position, but both have had issues with the latching mechanism over time. I also personally prefer the aesthetics of the Truxedo over the Bak.
Both options I had were easily removable as well, but the soft roller was much lighter, more compact, and easier to remove and store if needed.