I offroad a lot. A whooooole lot.
And that video doesn't really make a point because the sample size is so small. He used a very good car to begin with.
This game includes a specific bar, called a traction bar. You will notice that traction bar doesnt move at all when you customize your vehicle and look at the list in your garage.
Which the argument for the Sandking, is it has stock off road tires. LARGE ones at that, and it makes great power, the problem is that R* decided it was to cursed with a low traction stat. Which is why it is very ineffective at offroading unless you are water fording, or dune hopping. The traction stat is also what gives prevalence to the stupid crap that is a sports car, clawing its way up a mountain side, no matter what tires are on it, same with sports bikes.
The top 3 super cars all have phenominal traction stats, the highest in the game, and as such, they will always out climb any of the trucks.
I wish they had carried over the way the cars behaved from IV. With a bit of tweaking to remove the extreme body roll. Because cars in IV had mass, they had traction without having a skewed stat to determine whether it was a faggio or a entity. You could grab an suv and plow through traffic like they were children in line at the store, now, you can barely even push a blista compact out of your way, or even plow a cop car out from in front of you as they do that stupid get in front and slam on the brakes crap.
Rockstar took no heed on the concept of gearing, ground clearance, approach, departure, or even the fact that when climbing a hill your car constantly wants to shift into the higher gear which causes you to lose momentum.
Point of all this being, offroad vehicles in this game should do one thing extremely well, and that's offroad, and frankly, they dont. With non existant 4x4, couple with the traction coefficient they modeled in, supers and sports will always outclimb everything else. Period.
The Sandking and the MW mesa are outfitted for offroad prowess, and they both fall flat on their faces when confronted with an environment one would use them in like their real life counter parts would be.
The tires, while maybe making a small difference, it isnt' noticeable enough on all applications. Like you should be able to drastically change the characteristics of a vehicles handling with a different tire package, and it just doesnt happen significantly enough.