Snow tires make more difference than awd. All season tires are barely adequate to limp home in snow or on ice.

The XF is very good in the snow. The "winter" mode aids traction and the TRAC setting for the traction control adds another option, useful in deeper snow.

The trouble with awd is it does nothing for braking or steering. Traction for getting going really isn't important in winter because if you cannot stop or steer you will crash.

I drive in severe winter conditions every year. I drive my XF, a SAAB Turbo, an Alfa Romeo 164 and an Audi S4. The best car for winter is the SAAB with the Alfa close behind. The XF is fine. The Audi had great traction but the handling leaves a lot to be desired. The Audi will understeer right off the road if you are not aware of the characteristics of awd.

 

Agree that (good) snow tyres are most important. Do make sure you get tyres that are designed for the conditions you meet (low) temperature wise and snow/slush/rain wise. Tyres for the former will have softer compounds than the latter and neither will be optimal for the other set of conditions.

AWD helps a lot for traction simply because all four patches of rubber pull instead of one pair being pushed/pulled. I have put it to the test on a short hill climb as follows: Rear Wheel Drive (RWD) with Traction Control (TC), and (otherwise identical) RWD vs AWD both without TC. The RWD car with TC switched off was a bit better than the RWD without TC mainly through tyres and to some extent more sophisticated suspension. RWD with TC was better but I could do nearly as well when really babying/using some spin to my advantage. The AWD left them all well and truly behind. In deep snow, two feet, only AWD will do.

A sophisticated AWD (Limited Slip (LS) front/rear diffs and LS or automatically locking centre diff) is better braking as well: No wheel can lock without the others locking as well, which both helps get the most from the traction available and helps stability.

Finally, the torque split is too simplistic in just about all AWD systems which sees most AWDs careening off when you overcook it

It should be said though that most (all? haven't checked lately) current AWD systems on sale are nowhere near as sophisticated as described, many of them even (manually selected) part time.

 

Get some winter tires for the car or find another car to drive in the winter. I saw a Chrysler 300C SRT-8 get stuck on a slight slope the other day. He caused a enormous traffic jam on a main highway. He slowed down to get over while going up hill and then sat there and spun. A friend of ours drove by the area 2 hours later and he was still stuck waiting for a tow truck.

Winter tires for my stock 20" rims are in the $2k range so I opted to drive another car I have. However, I did drive the Jag to work today and snow mode does work better than I would have expected.

 

In that case it would be the tires. All seasons are bad enough but summer tires are hopeless. Awd with summer tires is hopeless also.