So we purchased a brand new, 2018 JLU Rubicon exactly one week ago. Officially name "The Step Child", we slapped 35" Cooper STT Pro tires and 1.5" wheel spacers on her but left her otherwise completely stock.
We then immediately took her out to Old Chinaman Gulch in Colorado and tested her on every obstacle we came across.
When all was said and done - we had a smorgasbord of scratches and gouges on the belly pans and sliders (that's what they're there for) and zero actual body damage. The only thing that stopped the vehicle at any point was clearance (which can be easily fixed with 37s and a lift), otherwise it climbed just about anything you put it up against.
All in all, we were extremely impressed with the offroad capabilities of the vehicle. Ultimately this thing is a beast right out of the box - 10/10 I would recommend to anyone looking for a vehicle that's comfortable as hell on the road and can handle itself with flying colors offroad.