[grill-n-go]

We have neither. A shell seemed like it would provide plenty of room for stuff under locked cover while a solid tonneau would subtantially limit the size of stuff that can go in the bed. The retractable tonneaus appeared to be a good compromise until I considered what we do with our truck bed.

We occasionally transport objects which are taller than the bed is deep (eliminated the tonneau), regularly transport lots (30+ objects) which required stacking, and arranging in the bed in such a way that a shell would make the task much more difficult. If I had a shell, I'd have to crawl inside to load and arrange. With a shell you can only get at the bed through the tailgate really limiting access to the bed.

For camping we take:
2 Kayaks 13.5' each
2 sets of (paddles, PFD, seats, etc)
2 bicycles
1 generator
1 Weber grill
1 30 Gal. tote
1 tools (i.e. drill to raise/lower stabilizers, level, etc.)
1 ea water, gasoline containers

The bed holds a Kayak rack and a bicycle rack, which would get in the way of a retractable tonneau. We've since gotten a saddle type box, but this is not a necessity. When I'm feeling paranoid I run a single chain through everything. In the begining I really wanted a shell, DW said a truck is not a truck if you put shell on it.