I've always been an "enclosed" guy, but that's partly due to wanting extra storage space inside the trailer to be able to lock up spare wheels and tires, jacks and tools for weekend track ventures. The car is obviously much more protected during travel, and arriving "clean" and ready to go can also be a big benefit.
If you're interested, I'm getting a new one and have my fancy, red 20' Pace for sale in the Viper classifieds. It's already set up and ready to go for a Viper. I'm asking around $2,000 more than a new, open "roll back" will run you. It really all depends on your circumstances and preference.
As far as your tow vehicle is concerned, the weight factor is an important consideration. That's the reason I went with a 20' rather than the more typical 24', with 4 wheel electric brakes. The 20' was WAY less weight than the 24, and my loaded towing weight with the Viper usually comes in about 6,800 pounds. I've pulled all over the country with my little 97 V8 Dakota, which was rated for that much back then. However, just to be safe, I still use an equalizer, weight distributing hitch, and an optional sway controller. I strongly recommend that for towing most anything if you're going to be doing a lot of it. Hope this helps.