I'll go point by point w/ you (but more briefly)
Interior: Subjective, pick for yourself.
Winner: Too subjective to pick
Towing: KJ has more power, so will pull loads easier. Both rated at 5000 lbs, though, and Xterra has a truck frame.
Winner: KJ
Offroad Ability: Pretty much the same, but I'd say the Xterra ('cause I'm not a neutral observer).
Winner: Too close to call
Suspension: KJ has coils, so more "car-like" on road ride. Xterra has leaf/torsion. Flex is similar. Up front the KJ's LCA's are literally less than 6" off the ground stock.
Winner: Ehh, why split hairs, neither one handles very well and flex is similar.
Axles: If memory serves me, the KJ is a D35. The Xterra's axles are more comparable to a D44 (I think I saw somewhere they were a bit beefier, but still close).
Winner: Xterra
Frame: KJ is unibody, so it's weaker. Xterra is truck frame, so it's more durable.
Winner: Xterra
Reliability: Crap shoot if you're unlucky, but your odds are much better w/ an Xterra.
Winner: Xterra
Overall winner: You decide.
Thanks for swinging by Tom!