Like everyone has said, nothing is best, everyone wheels what they can afford and what fits their wheeling style.
I wheel a full-size Dodge Ramcharger (I'm a Dodge guy). Wheeling a full-size has it's drawbacks, size, weight, size, width, size and height.
But it has it's advantages too. They can be dirt cheap, and I mean dirt cheap. They come with many of the drivetrain parts that most people in Jeeps or Toys eventually upgrade too (axles, V8, ect..). Plus, when I do upgrade, one ton parts are a direct bolt in. I also have all of the suspension, transfercase, gear, locker, axle, engine and tranny upgrades I could ever need available to me. Also, I have room to haul everything I want with me. Many full-size trucks can fit 33" tires with minor fender trimming. Bigger tires are just a mild lift (or more trimming) away, thats easy with leaf springs front and rear.
I've wheeled with Jeeps, Toys, Sammys, and other full-sizes. There are obstacles that the smaller rigs walk, and the full-sizes struggle. There is also obstacles that the smaller rigs really struggle on, and the full-sizes can walk them.
The full-size trucks, especially Dodges, don't have as much aftermarket support as Jeeps, or Toys, but part of the Dodge mentality is adapting and fabricating. And since when was "bolt-on" hardcore anyways?
In reality, when anyone gets real hardcore, it really doesn't matter much what you start with. By that time, you've swapped out so much for a better mix of parts, what you started with really doesn't exist anymore.
And a particular side bonus for me wheeling the RC... About 80% of the parts on my Ramcharger are interchangable with my tow rig (1975 W200) as they share an almost identical drivetrain. This is great if one of them breaks a long way from home.