Rancher XL sucks. It might have good speed for an off roader but there's nothing else good about it. Spend quite a while looking for one, then ended up selling it after realising how terrible it was. It's better than the Merryweather Mesa though; that thing is just terrible.
Rancher XL is the best for handling and breaking in mud/snow or raind and also has good top speed and with max accel it goes on top of a mountain easy, i have one fully modded in my gta online garage and i climbed like half of mount chilliad with rancher xl and had 0 problems.
And trevor's truck is the best for ramming if you have those metal bumpers in the front and it has a lot of resistance, i tried with my friend 2 things the reinforced glass in the front and resistance with a tank falling on top of it, my friend shot me and i didn't take any damage with the glasses, and then my friend stole a cargobob and hooked his tank and dropped it on top of trevor's truck(i had 100% armour on it) and it didn't got smashed or exploded, best off road to take to the middle of a war.