I like the Mantec style (bent DOM round tube) carriers, not the kind made from square tubing with lots of hard angles. That--to me--is the Defender style.
For my needs, the ideal, trail-focused carrier is built like the Mantec but made much heavy duty and able to hold a 8.25R16 Michelin XZL tire on a heavy steel wheel. I want the rack to have a solid mount that puts most of the weight on the rear cross member but also ties into the tub of the truck on both sides of the tailgate. In other words, when the tailgate is closed, I want part of the weight to be distributed to the tub (or crossmember) on the opposite side. This would need some sort of hard rubber block for it to rest on so that things don't vibrate.
I don't want any fuel can carriers and I wouldn't mount my Hi-Lift there because I want to be able to retrieve the jack in the event that the truck slides back into a rock face and pins the rear carrier.