I think I prefer lowercase. It becomes "Earth-bin" rather than "Earth Bin".
π bin, or Earth-bin, sounds to be like a universal take on the kbin/mbin network. In the end they're both *bins; Replacing the * with π makes this website πbin.
π Bin, or Earth Bin, sounds to me like a garbage can for the earth.
The difference is obviously not that huge, but that's my intuition at least. :)
Thanks :) I thought Mbin π sounded a little weird, and the domain is still technically kbin.earth, so I could have stuck with Kbin π, but π bin is a nice mix.