An XC70 has the same towing recommendation as the V70 (1500 kg), 1600 kg Europe(!), but it's heavier, meaning that it will use more power moving the car, and taller, meaning that the trailer can get more leverage over it and possibly push it around more. How much trailer are you pulling? (length, height, loaded weight)

For on-road use, an S60 or V70 (fwd) is probably a more stable, reliable, and economical car. If traction is sometimes a problem, e.g. while pulling the loaded bread trailer on snow, a weight-distributing set-up might be a solution. If you need to find someone to build you a Class 3 hitch, let me know. I have one on my car.