isnt there more room in a truck bed tent or is the bed needed to haul more stuff?
It's not a question of "room", its all about convenience and comfort. There's more room in a 10 person ground tent.
I had a smittybilt roof top tent, purely for the fact that I could sleep where I parked. Finding a flat, smooth area to drop a tent in the middle of a rock infested desert is not easy or even an option sometimes. Or if you can find smooth, it's likely not flat and vice versa. With the RTT, just drive up on a rock and self level the truck, open up and you're sleeping comfortably. Being off the ground is another nice feature.
I now sleep in the bed of the truck, on a 2/3 width drawer/platform with a camper shell. 1/2 the head space, but cant beat a solid wall cave when it's blowing 30+mph all night.
LOTS of companies out there. Figure out what you want out of the tent and your budget, then go from there. CVT and Tepui are pricey, but great quality. Smittybilt is probably the cheapest one and if I were to buy another, i'd throw a little more coin and step up to a Tepui. If I had a garage door with enough height and money, I would do a wedge style cab-over camper like the Vagabond Drifter or the GoFast Camper. Knocks out a camper shell and RTT in the same purchase.
Dont forget to factor in a bed rack to hold the tent as well. That is often overlooked and depending on your taste, can be very expensive on it's own.