Hello, fellow Oregonian!
330i will handle better. It comes with a sport suspension, sits lower and has lower profile tires (assuming SP).
Even in the wet the "i" model is better than the "Xi". BMW AWD system is not intelligent, like Quattro, ATTESSA, HICAS or the one Porsche is using. BMW has a permanent power distribution, not adaptable to the driving conditions, like the others. I drove both and did not enjoy the "Xi" as much as the "i".
Acceleration will be slower once you moved off the line due to higher weight of the Xi models. Car magazines managed to get better 0-60 numbers for the AWD, but not without dumping the clutch at 6000RPM.
Unless you drive in the snow often, AWD BMW is not necessary. If you do occasional skiing trip and such, just get a set of Snow tires and you'll be fine.