I run 180mm cranks on my free wheel road bike and 172-175mm (172 now and spring, 175 in the summer) cranks on my fixed. I use my fixed like a regular bike on open roads so cornering isn't much of a problem. I slow down on tight corners .
I like the longer cranks for climbing and I am 6'4" so longer cranks feel more natural for me.
It is interesting to run the same gear with different length crank arms. You lose some of your spin but climbing is easier. For spinning though shorter crank arms are the way to go.
You should experiment, especially with a TT setup. I think for TT a longer crank arm may suit you.