the first gen xi had the first gen xDrive, which i think was derived from the x5's system, where the split was fixed 62 rear, 38 front.
when they came out w/ the x3, they revised the xDrive so torque wouldn't be fixed at 38/62 split. the torque could be delivered to the wheel w/ most traction, or something like that, and the x5 starting 04 has that system.
anyway, i heard that they'll be phasing out the xi in favor of the x3. or was it just the XiT?
either way, if you want a awd ride, audi has one of the best awd systems. but test drive teh xi, the quatro, and maybe even the saab 9-2 among other rides before deciding. how much are you looking to spend?