Unless you have strangely short legs, excellent low-light vision, and a great tolerance for an irritating lack of power, I hope you're looking at the '05+ Xterra. The old one has a door panel and console that will rub your knees raw within 30 minutes, guages that are about 30 feet down a dark tunnel, and one of the most pathetic power-to-weight ratios since the 2.5L XJs. It's an awful time. Would probably be a good vehicle for a chick, since they're normally short (eliminating the leg problem) and place looks over function (eliminating the horrible lack of power problem,) but not for most guys. The '05+, however, is AWESOME. That new 4L is tons of fun, they carved out the door panel and slimmed the console, and it's longer and wider adding even more room. Add to that the cool plastic cargo area and other nifty features, and it's the most appealing mid-size SUV in my eyes.
If you're considering the old one, I urge you to take it for a test drive that lasts an hour or so if they'll let you. You'll find your ass is asleep, at least one of your knees has a sore spot, and you're worn out from shifting your legs back and forth. The ergonomics are just terrible for anyone over 5'5".