Older games have basically doubled in cost over the past 6-7 years which makes Stern Pros a better value in comparison. My limit on old games is $3500. Anything more than that and I'll save a bit more and get a Stern. The software and replay value is just better on a Stern and they don't require much maintenance and are pretty trouble free.
The other side of it is that I've been collecting for 15 years and have owned or played most of the 90s games to death so Stern Pros have more appeal to me in the $4k-$5k market.