My only advice is to stay away from the Polar CS series. My wife and I just bought the CS200. Hers wouldn't register the cadence all the time. It would stop periodically and then just start back up on its own. Her heart rate monitor was sketchy too. Mine woulnd't register the speed AT ALL. It never worked. My cadence was fine. The heart rate came and went a couple of times. I had put stronger magnets on them before we left out but that didn't help at all.
After I had ordered them I started doing a google search--a little backward but that's just me! I found lots of folks having trouble with sensors not working. I was hoping ours would come in and everything would be just fine. Oh well...
We made one 32 mile ride and took them back to Performance. They were great about taking them back with no hassle!
I am putting our Trek incite 9i's back on. We have had NO problems with those. Too bad they don't do cadence or heart rate...