Overall I think the 4.0 is better engine for longevity and for some styles of off roading. I have a 3.6 JKUR and the 4.0 is much better at low torque. Each are a 6sp manual and I prefer the LJ for crawling or even steep climbs, the 3.6 just doesn’t have the low end torque. The JK is much nicer for road trips, and quieter.
Agree 100%. I've rented 3.6 JLs and JTs for both off-road and highway use. It's awesome having enough power to get out of your own way but I found myself having to really rev the 3.6 to get up inclines that I practically idle up with the 4.0.