Depends how you're going to use it.
I have a tri-fold on my truck, my dad has the single piece hard-top tonneau that pops up with gas struts.
His is better in terms of security, and weather protection of stuff in the back. But it's useless if you want to use the truck bed for tall bulky items (IE appliances) or things you need to load from the top, IE A load of dirt/gravel. The downside is that tri-folds can be easily broken into by jamming a screwdriver in at the back and pushing down on the release cable
My dad's truck is a pavement princess that has never had dirt in the back, (the plastic bed liner is literally shiny as new. Mine has had many loads of dirt & mulch in the back, along with big items that I've folded the tonneau up many, many times. I'd say we have the appropriate tonneau's for each of our purposes:
