The Garmin Forerunner 305 is awesome. I just love it! It has so many great features. The only downside to this product is the size, I would like for it to be smaller. The Forerunner 405 is smaller but it doesn't have some of the features I like on the 305, like a button to access the backlight and the 405 has a dial instead of buttons...I like the buttons best. When wearing the 305, the size doesn't bother me, it just looks clunky. Hope this helps!