I had a S70 and traded for an S80 and a S60. While the S70 had a larger rear seat area and smaller front seat area (comparing them both) I welcomed the larger front seat area in the S60 and was willing to give up room in the back. I seldom have rear passengers and when I do then I move the front passenger seat up a bit and that gives the taller rear seat passenger some more room. I feel it's a good tradeoff. Another thought-if you have unruly children you can reach them easier with the smaller rear seat area!!!
The S80 had 'oodles' of room in the rear but the car does ride a little soft which some people like. The S80 is more of a luxury bent car.