4 plasma, 2 carbon, 2 polished, 1 x-metal so I guess my favourite is plasma. Not sure I'd put the finishes in that order mind - probably I'd go plasma>x-metal>carbon>polished.
For me it depends on the lens and what I may be wearing or going to. However, I reach most often for my R1s in Xmetal, and even more so soon with a violet lens and linegear violet kit about to be installed.