Bike fit / correct riding position

Whilst I agree that optimal length differs (by individual and by intended use), my question is whether consistency across bikes yielded any performance benefits when the purpose is to train for a given purpose (rather than use each bike for a distinct purpose). I'm inclined to go for a 170mm road crank I think.

I'm sensitive to small adjustments in bike fit. When I made the change to 170's across my bikes it made a massive difference to how I felt on the bike. Especially at high cadence.

I couldn't tell you if that actually improved my performance, there are far too many other variables to that, but it did make me marginally happier.

By the way, I've got a spare 170mm track crankset you can try out.