I really had not considered a JKU. I'll check them out. I just need it to comfortably seat four full size adults on a 4-6 hour road trip. I'm 6' and weigh about 220. I need to be comfortable in the rear just in case I have to ride back there.
The rear seats in the Commander are firm but comfortable, more comfortable than the rear seats in my JKU. They were about the only thing I really liked about the Commander. The 3rd row seats however are useless for anybody above 4.5'.The Grand's have a bit more room in the back seat, but for 'cross country comfort' in a Jeep, you need to look at the JKU, possibly the Commander. (I have never seen a Commander up close, but have heard the back seats(middle seats??) are not much better than an XJ)
My only gripe with the rear seats in the JKU's is they are to upright. Plenty of legroom for me, I'm 6'1" but I like a little recline in my seating position.