After watching 'King of the Hammers' type racing, or even the Baha races it is clear that the new breed of UTVs are able to out run even the Ultra4 rigs in many cases. 2019 (I think) Can-Am brought their latest and greatest, swapped in better tires, and ran the piss out of the 'Hammers. They have much better acceleration, ground clearance, even fuel consumption.
Not having the constraints of being road legal helps them outperform our old school Jeeps. (Unfortunately)
The kids just don't seem to like the 'slow and steady' anymore. Other than as a work vehicle (off in the cow pastures fixing fences) I couldn't justify the cost for such a limited use vehicle, but they are impressive.