The issue that you raise about AWD is not Volvo specific. Any AWD car is going to have problems with different tire sizes. That means that you run the risk of having to buy four new tires if one is damaged, and the other three have more than about 20 - 25,000 miles on them.

You should ask your wife to be objective and ask herself if she REALLY needs an SUV or AWD, or if she is just following fashion. Now that gas is permanently high and will only go higher, the SUV craze is about to end. In snow country, AWD is nice to have, and probably you can justify having it. But traction control is probably more important, for safety reasons, and 2 WD with traction control might be enough for an experienced driver that has to deal with snow only occasionally.

I get the impression that European cars in general have become more trouble prone over the last few years. A 2005 or 2006 XC is probably a decent car, although, I would seriously try to find out why a 2005 or 2006 car was for sale used. Either it's a used (and abused) rental car, or there was something about it that made the owner want to get rid of it. Perhaps you can find a used dealer loaner car, or factory executive car. But go into it with your eyes wide open.