My vote is for a UTV. But then I have a winch on mine. Having a winch guarantees you that you wont get stuck.
A small correction if I may...
A winch doesn't guarantee you won't get stuck any more than an umbrella guarantees it won't rain. A winch CAN help make sure you don't remain stuck. Of course, don't go into a mud hole without a suitable winch point in reach or you are just screwed.
To answer the question, at our ranch we have 4x4s, tractors, dozers, UTVs and ATV's. When it is muddy, we leave all the heavy stuff put up and use the ATVs and UTVs. They simply are better for the job. They go through the soft stuff better and don't tear the place up. Nothing pisses off a landowner more than ruts everywhere after a rain. We lease one piece of our property to hunters. If they brought in modded off-road trucks and tore the place up, we would have new hunters next year.