I went to Blackbox because its UI elements were smaller (title bars are more narrow, no 64x64 dock icons) which gave me more real estate on my 1024x768 monitor.

I went to Blackbox because its UI elements were smaller (title bars are more narrow, no 64x64 dock icons) which gave me more real estate on my 1024x768 monitor. I then migrated to Openbox because that had more active development at the time. This year, I've switched to herbstluftwm, a tiling window manager that's really nice and works in a way that agrees with me.