I have had a truck topper (we call them caps around here) and a tonneau cover. As nice as bot are I always end up liking an open bed best. When I had the cap, it was very light, all aluminum so I could put it on and remove it by myself. They are very handy in the winter and also when combined with a locking tailgate anything inside can be secured. My tonneau cover wasn't one of the fancy tri fold ones. Every time I open it up I have to undo snaps and in the winter it shrinks and is a pain in the a**! If you go with the tonneau cover get a trifold! They are worth it.
The utility cap with the side access looks like a great idea! Keep the small stuff in the sides and leave your bed available for larger items.