When I replace my stationary bike (a high-quality Tunturi, which has lasted many years), is it better to replace it with another upright stationary bike or a recumbent bike? Or is it a matter of personal preference?
It depends on how you use the bike for cardio - interval training or long slow distance - as well as individual comfort. I use the exercise bike strictly for interval cardio, and even then as a third option behind the stepmill and the elliptical machine. Despite the discomfort for me, no cardio fries the quads like a bike. Many distance runners have found cycling useful for bringing their relatively weak quads up to the level of their hamstrings.
There is little doubt that upright cycles allow for greater force generation, which is why you won't see recumbent bikes in races. But the upright position can lead to discomfort in the crotch (and worse
) if done for long periods of time. That's the reason why recumbents were introduced in the first place. But the crotch problems seem to be more of an issue for some people than others. Lance Armstrong, for instance, hasn't suffered physically despite all the time he spends on the bike. Your sticking with cycling for 12 years probably puts you in the problem free group.
If you've had good experiences with your Tunturi bike, it would make sense for you to look at Tunturi's newer equipment. Tunturi has a good reputation and they make good products.