Which should I use?

I have both a Garmin Edge 520 and also a Samsung Galaxy S7. I would need to buy a mount for one or the other. Which is preferred?

Garmin. It is a better bike computer for outdoor riding.

I tried the app on a Galaxy S5 yesterday and the GPS cut out half way through without any battery-saving mode being switched on. There was some weird data in the activity log, too, which seems to get resolved between the app and the website (e.g, average cadence much too low, average power low, max heart rate about 30 bpm too high). Other than that, I enjoyed the app, but the Edge 520 has to be more reliable.