If you do long, expedition style wheeling or family wheeling how are you going to pack a Rubicon? Thats possibly the biggest issue. Remember a stock Rubicon has TERRIBLE ground clearence and needs lifted ASAP.
As far as water fording No way, I dont know how they measure but knowing how US built vehicle intake systems are there is no way a Rubicon can touch an Xterra.

As far Approach Departure, remember the 05 Xterra has a knuckle dragger front bumper required by new federal regulations, but once replaced with an off-road bumper I would bet it challenges the Rubicon.
Overall a Rubicon would be more capable just based on wheelbase, if your entire goal is extreme rock crawling, and of course solid front axle. BUT, for long trips....Its all a compromise. I run everything from easy to VERY extreme, and a chose an 05x as my next build up.