OTOH, a spin bike is not a road bike. They're all fixed gear. Unless you have been riding a FG bike some of the time, there's a neuromuscular learning curve to FG, even a spin bike. My wife and I did weekly spin classes for 2-3 years. It was fun, but we finally quit because #1, they were FG and thus not the same to pedal, and #2, we wanted to do normal road bike training, you know, long moderate steady state, intervals, varying cadence workouts, OLP, all the usual stuff on does on a trainer or resistance rollers.
There is the attraction of the group fun and pain in spin class though, so whatever gets you on a bike more often and for longer is good. We wound up liking not driving anywhere, as riding at home was quicker. Another attraction of spin class was that we'd always hit the weight room after class, which worked really well. Older now, we can't do as much volume per day, so we don't do that anymore. It was great in our 50s and 60s though. Highly recommended. Not the same type of contractions and different range of motion. Spin class didn't impact our weight training, though we always joked, "How we gonna walk to the car now?" Weight work really helps with endurance cycling.
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