Garmin Connect is doing this pretty well now -- comparing an activity against your personal best over varying time frames. But with theirs you can't determine which in which activity you had the better power... unless you run the "Full Report" which only looks at personal bests across all activities. In my case, I have a bunch of older bogus power data from when I was using a PowerTap PowerCal and had no real power meter. Garmin gives me no way to exclude this data from my personal best calculations.
Allan
Garmin Connect is doing this pretty well now -- comparing an activity against your personal best over varying time frames. But with theirs you can't determine which in which activity you had the better power... unless you run the "Full Report" which only looks at personal bests across all activities. In my case, I have a bunch of older bogus power data from when I was using a PowerTap PowerCal and had no real power meter. Garmin gives me no way to exclude this data from my personal best calculations.