I am not familiar with the Gymboss. However the Garmin came highly recommended from numerous different sources that regularly run marathons and triathlons. My brother actually bought this for me as a gift because we have all been training for a marathon and he was tired of me guessing my mileage and pace. I have only used the run feature and it works great. It beeps at every mile and lets you know your last mile pace. I love the watch. I ran the marathon and the battery last the entire time. It took my one brother 6+ hours to complete and his Garmin lasted the entire time. Hope this helps you out.