Alot of it depends on if you'ld prefer RWD vs FWD because the two cars are totally different.
My experience with older turbo 4 cyls (red motors) made before '93, the year they added piston cooling and other minor improvements, is that unless the oil was changed very often and not driven hard, the piston to wall clearance becomes excessive and they typically develope a piston knock usually heard with a hot engine at idle. It'll sound like a diesel in more extreme cases. Although they'll last along time like that, it may not last an extra 100K miles w/o attention, usually costly. I have an older 745T wagon myself and it's a great car with 210K miles on it but it's had its share of parts replaced over the years too, including a new engine. I plan to keep that car for at least another 10 years, the body and interior are still perfect and it's mechanically perfect now.
Now, 850s are well known now for slow leaking AC evaporators (the #1 problem with its AC system) and replacing them is a big job (about $1,200 total) so if the car you're looking at still has its original evap, chances are good that it might leak slowly. See if there's an AC dye sticker attached under the hood as that indicates that it was low on freon at least once and that AC dye was added for leak detection. If it were my car, I'd just get it topped off every year as that's usually how slowly they leak.
My ideal used Volvo choice now would be a '96-'97 turbo 850R wagon but it'll be more costly to purchase than the cars you're looking at now.
Don't get me wrong, both cars you're looking at could be very decent used Volvos but both are known for a few possible problems which could be costly to repair someday.
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