The Nike C series is quite good. Just as good as the Polar series. The Nike is more user friendly, but the Polar may offer a few more features. The C8 differs from the C10 by the amount of lap splits, which the C10 has 100 lap splits as opposed to 50 with the C8. The C10 is coded, which means it won't interfere with other heart rate monitors in the area. The Polar is unrepairable. And if you don't get the new models, which are slightly more expensive than the Nike, then you have to send the band back to Polar for a whole new band, because the geniuses at Polar decided not to offer a simple battery hatch in the back of the strap. Nike's all have that battery hatch and are fairly easy to change. But don't change the battery on your own during the warranty phase, for it will invalidate the warranty. Polar is accurate though. But don't listen to Nike nay-sayers who are unjustifiably anti-Nike because they think Polar isn't similarily a large corporation behaving like a large corporation. (The C8 is the first Nike in the series that offers lap memory)