Sales numbers talk, happy customers walk. Fitbit sells tons (likely 10x that of Garmin), while they are poorly rated. Garmin really doesn't as much even though their products are quite well liked.
Its closer than you might think - Fitbit did $1.5B in rev last year. Haven't check their filings but presumably thats almost all from their devices. Garmin did $858m in rev last year from their "fitness" segment. Plus some fraction of their $809m "outdoor" segment includes the Fenix line, which is also in the same category. So probably $1B+ total
