Wattage based riding is a great metric for training. HR is nice, but you can experience HR drift during an interval, but watts don't lie. You're either doing the prescribed wattage or you're not.
I'm not a huge fan of their leaderboards only using kJ because that's not a real indicator of fitness. A big guy can push huge watts and a lot of kJ, but their watts / kilogram may not be as high as someone that's lighter. I always turn it off when riding.
The key is to retest your FTP every 4-6 weeks to make sure you're working in the right zone. There are similar tests for HR, but once you go watts, you never go back.
I'm not a huge fan of their leaderboards only using kJ because that's not a real indicator of fitness. A big guy can push huge watts and a lot of kJ, but their watts / kilogram may not be as high as someone that's lighter. I always turn it off when riding.
The key is to retest your FTP every 4-6 weeks to make sure you're working in the right zone. There are similar tests for HR, but once you go watts, you never go back.