RunKeeper is the best so far plus the fact that my running mates are all using them. It surely is easy to use and their web UI is of good design, e.g. my old eyes like their large fonts. It may not be the best in the market as there are many apps fighting for the space.
iSmoothRun is another app that I have read about in forum, it’s not free like RunKeeper (there is no free version anymore the Pro version is now free). iSmoothRun is surely feature rich and the key difference to me is that “Your data are yours”, i.e. data are kept in the iPhone.
TrainingPeaks may be originally designed for very serious athletes and coaches, typically if I couldn’t figure out at the first 5 seconds how to navigate and use it, that isn’t my cup of tea.
RunningFreeOnline is slightly better I managed to upload GPX/TCX files as a trial. The graphs and web UI design looks a bit outdated maybe it has been around for a long time. Updating the web UI is pretty risky as many users may have locked into the look and feel of the site. I’m also puzzled to see the data blackouts (straight lines between 2 points) in the curves. Again its UI is pretty old fashion to me.
I’m not new to dailymile I tried that a while ago before I use RunKeeper. Its interface is of modern design (fast loading, ajax etc) and nice looking. Site navigation is easy, you even have a few color themes to choose from. The Garmin (beta) and Nike+ sync feature is impressive and it works well for me. The drawbacks at the moment are that heart rate data isn’t sync’ed from Garmin and only about a dozen or so workouts can be sync’ed. I can see that dailymile is pretty popular.
I’ll be using iSmoothRun from now on to test it out. At the moment I prefer uploading GPX file to RunKeeper to share with my friends. Dailymile has a drawback if you care about privacy, i.e. they have no privacy control whatsoever and everything is shared to the world.