I'm on the same page right now, also looking for an SUV for winter and have only my gf and a cat to drive with so don't really need a full size one (X5/Q7).
BMW X3 - I really like the new styling of X3 but that's only because it looks more like a X5 now. It has a great xdrive and also very nice fuel consumtion with the smaller diesel engine. Only reason why I don't like this car is the X5. The X3 will always be the baby-X5 or woman-SUV if you prefer.
BMW X5 - no real disadvantages other than the price tag of 100k EUR for the one I would actually like.
Audi Q5 - I ruled out Audis because of the ridiculous quattro system they are using (youtube -> X3 vs Q5).
Porsche Cayenne - price tag and most expensive to own in the long term. Dunno why I have the feeling that to own this car I would first have to buy a 911 so it doesn't look like I wanted a Porsche so badly that I bought the ugliest one
Range Rover Evoque - my favorite so far, just not sure about the reliability as it is with Range Rovers.
Bottom line is that I will probably go for either the Evoque or a Premium Selection X5.