I saw a discussion thread on the wattage email forum recently that went into this. Bottom line was there are a lot of assumptions built into the algorithms to convert HR data to Kcal, so their usefulness for calorie counting may be limited. Over time, you may be able to figure out which of the three is the most consistent (it may be wrong, but it's wrong the same direction and amount) and use that for tracking purposes. Me - I would just ride and walk lots, clean up my diet, and not worry about it too much. And use body measurements (girth at various points, or just how the fit of clothes changes) and track performance on the bike (time, HR, and RPE for the same route under similar conditions) to follow improvement. I found that when I started riding, setting a goal (in my case it was a century ride) gave me a better focus for riding than "lose weight". Good luck.