I really like the Alta HR's slim, stealthy design with the Special Edition gunmetal version definitely being my fitness tracker of choice. Fitbit has done an excellent job creating a less is more fitness band that is comfortable to wear with solid features and specs.
Slim & stylish form factor; Excellent app & fitness ecosystem; Solid build quality; Does basic features well; Sweat-proof; Easy to swap out bands
Expensive; Lacking a few nice-to-have features