I noticed a bit of difference going from 165 to 170 (I ride 175 on road but our track 'dislikes' long cranks), but it wasn't huge and I can't say it had an effect on my times that I could notice. I change gearing a lot though so its very possible I prefer a bigger gear now and a lower cadence, but I can't blame that 100% on the crank length.
I completely agree with the above, you cannot research your way to a correct answer. IMO, and it may be disagreed with, crank length makes very little difference to the majority of people (talking 2.5-5mm changes, not 160s vs 180s).