As I think of it, I really cannot come up with any solid features for the 850 series over the 760. It's a newer design, but it's smaller. Newer engines, more powerful engines, but then again 760's B230FT & B280 are quite durable. FWD vs RWD, more a matter of preference. Visual appearance, well, same thing. To me a 760 has that "Bloody Yuppie Volvo" charm, 850 says to me "2.4 kids & a dog going on a sunday picnic".

I wouldn't start changing vehicles, especially to one that doesn't feel as good, just because it's "newer". Generally you have a very good idea of what you have, who knows what kind of a ticking timebomb that other vehicle might be?