I had a WRX for my daily driver. I ran blizzaks on it. The car was a damned animal in the snow. It would claw through snow as deep as the height of the hood. But E46 X-drive, like many other AWD systems, sounds better than it is. I went through this...getting rid of a snow beast, I went to a 330ci. I get around just fine in the snow with snow tires on the car.
If it's for your wife, forget about RWD handling and focus on the fact that E46 X-drive cars chew axles up regularly, use more gas, and weigh more. Weigh those attributes against what you find desirable about the RWD car. X-drive will get the car going from a stop better than RWD. X-drive will get the car up hills easier and with less drama. X-drive doesn't require any real driving skill or any real thought going into what you're doing. You just put the gas pedal down and steer the car. The electronics sort everything out for you.
RWD may require that you disable part or all of the DSC system to get it through certain conditions. If you turn the traction off on an open diff RWD car, you have to know what you're doing to some degree. It's not rocket science, and i'm sure you can teach her. My girlfriend now drives an 04 WRX. No traction, no electronics. I took her out in a big open parking lot. Within an hour she was drifting circles around light poles. It's not hard to learn car control.
The E46 330i will do just fine in the snow. I wouldn't throw her out there in it with all seasons and let her sink or swim. But put some good snow tires on it and let her throw it around in controlled conditions for a few hours, and she'll be just fine. DSC works brilliantly. It really does. I'm no race car driver. But i've been to my fair share of driving events and I know how to control a car. I know how to drive, and I leave DSC on nearly all the time. It actually saved my ass just this morning when I hit a patch of black ice on the highway doing 75. The car stepped out and slide out of line. It was too early in the morning for me to have a good chance of saving it without a lot of drama. DSC stepped in and righted the car very quickly.
I drive in the snow with the traction part disabled and the braking intervention on. At low speeds (or when I want to have some fun), I leave it off all the way. The car is perfectly capable. But even if you leave the electronics on, you can get around most of the time, and truth be told, the electronics are impeccable at keeping the car in line. When you're driving on a crowned road and the back end starts to slide and follow the crown without DSC, you can keep it on and it will use the braking intervention along with the diff's response to keep the back end in check. Don't sell the RWD car short because it only has 2 drive wheels.