I've only ever used Polar HRM's so far, so can't comment on other makes, but the Polar seems to work well for the HRM functions. If you want a HRM that also combines with a speed and/or cadence sensor then I have found the Polar ones to be very tempermental, slightest gust of wind and the speed stops working!
I think I read that Ken has a Garmin HRM that is very clever.
Depends on what you want function wise and what your budget is I guess.
I've not helped at all
