I think you just want to track both over the long term - that is compare your watch with your watch and your garmin with your garmin. But that is a huge gap, I

I think you just want to track both over the long term - that is compare your watch with your watch and your garmin with your garmin. But that is a huge gap, I think in general running creates more realistic VO2max data than cycling since there are too many factors at play (e.g. if you're in a group or not or using the drop vs. not).