Another BIG thing that separates the stock 4wd Xterra from the 2wd is:
"All Xterras feature healthy ground clearance, and the 4x2 versions are slightly higher than the 4x4s. The 4x2 XE rides 8.7 inches above the ground and the SE a full 9.2 inches. The 4x4 XE and SE provide 7.9 and 8.4 inches of clearance, respectively." Cars.com