With non-Apple Watches, you can't 1) reply to texts, 2) answer phone calls (or place calls), 3) interact with other native iPhone applications (like Apple Health).

You'll pry my Garmin from my cold, dead hands but there's no mistaking it for an actual "smart"-watch. I value it entirely for health & fitness, and the very few "smart" things it can do are just nice-to-have icing on the cake.