Which of these two new trucks would you choose

Kenworth. Time to put some beef behind those triaxles. Otherwise I choose the Volvo, provided you have a engine with beef but good agile like a mountain goat. Otherwise choose the KW.

My choice for your work would be a SD122 built at Freightliner to order. Or go to Oskkosch and see about them Army Surplus Tank transporter tractors something with a powered steer and a triple lockered drive axles under the 5th wheel back there. They tow 72 ton M1a2 v3 tanks with those routinely on any terrain.

I could be persuaded to pick up a tough Mack, if I can find one. But I refuse to get a truck that is all plastic and break in the morning frost in the coming winter. you might have a few V8 format Mack Superliner 500's still out there. If you can get one to beef the horsies and have a tri drive under the rear and so forth. I would take one out in a heart beat.It's not fast. But it will get your loads there.