The two (or three) things I’d consider are how much off roading/trail work you plan to do, and what weather conditions you plan to use it in. Cost is going to be bout the same, looking at $1,000 for a utility trailer and $1,000 for a tent vs $2,000 for an enclosed. I assume fuel economy will be a wash, the enclosed has more surface area but is likely more aerodynamic.
The more “off the beaten path” places you want to be able to take it, the worse the cargo trailer looks from a length/width/turning around/clearance/visibility standpoint. I have a 6x12 and to me that’s the minimum comfortable size for two people to be able to sleep inside it with room to stand up and dress, make a sandwich, store clothes, use a cassette toilet, and carry things like bikes and kayaks. If you go smaller it’s really just a sleeping pod.
However, one of the main reasons I wanted enclosed was the ability to camp when it’s hot out. It’s not a big deal to hike, bike, or fish when it’s 80-90 degrees out, but sleeping at 80 degrees is miserable, so I wanted to have AC. I also wanted to be able to pack up and leave it’s pouring rain without everything getting ruined or having to be set up again and dried out. The same could be said for camping in the snow.
The last (smaller) consideration is storage and alternative uses. Parking a RTT out in the yard here is likely to have mice, roaches, mildew, etc set in during periods of non use. It’s a toss up whether an open trailer or enclosed is more useful for stuff like moving furniture, hauling firewood, mowers, boats, and all that. Depends on what you’re doing.