Has any measured the relative performance of various mining software? I figure such a study would be very beneficial for all the miners to choose the most optimal software out there to squeeze out the most bang for their buck.
I think the closest thing is the bitcoin mining hardware comparison:
Miners have different performance with different hardware architectures, so which miner is fastest for you depends on which hardware you have (AMD GCN/VLIW4/VLIW5, NVIDIA, different FPGAs).
It might be an idea to start a wiki page for a mining software comparison. Alternatively, adding more measurements on the hardware page could do the same thing (but might bloat the page a bit).