Cordless, always!
My desk is always covered by whatever hardware I am working on at the time (I make prototype and proof of concept electronic equipment) and I found that a mouse with a wire just gets tangled up all of the time. Additionally, I swap mouse hands regularly (several times an hour) because it helps to keep the dreaded RSI at bay.
I have a few sets of rechargable AAA cells, a cheap charger and three cordless mice on the go. No conflicts seen.
Rans6......