IMDb vs Letterboxd

Why does Sol hate the owners of IMDb? Does it hurt Letterboxd that many of the best features are behind a paywall? Oh, and to get back to the topic at hand: which of these two services is better? Letterboxd and IMDb are like night and day. One is young, elegant and social, the other probably the most complete database of cinema that exists: so which of them wins? Which could we not live without, and where do they fall short? And what about the other film websites out there like iCheckMovies, Criticker and Filmchart? Can any of them measure up and do any of them offer up something IMDb and Letterboxd can't provide?