Originally Posted by DrWJODonnell

I have some experience with the polar power meter in the past. While it is good (IF YOU SET IT UP CORRECTLY), it is not great due to some variation depending on chain position (read: which gear you are in). It is a good way to get into power training and has the advantage of giving you race performance numbers which will tell you what you SHOULD have been doing in training. Race power numbers are very important to me.

Polar MAY be less expensive, but only if you already have an HRM like the 720i or the 725. While I like the software that polar has (and I still use it regularly for my rides even though I have not used a polar power meter for some time), you will probably want to pick up the $99 cycling peaks software (a new build that will be much superior comes out at the end of this year, but don't wait...the info in there is too valuable even now). So tack on th $99 regardless of what power meter you get.

PT is nice but is limited to racing or training, and for me using a TT disc was never an option. While good, my understanding is that in the cold and in the water it gets a bit flakey. And there is no elevation/climb data like you have with Polar. Still, if you look at it's expense versus the polar power meter plus the watch, you will find that they are not that far off in price.

Lastly, as a side note, a teammate of mine has been running the IBike power meter along side of his Power tap for about 2000 miles now and he says it is spot on with the power tap. In addition, the I bike is $500 and thus the cheapest (assuming you don't have the polar watch). Also, you can get virtual frontal area measurements (important for TTing). The disadvantage seems to be no use on the trainer and for a TT bike your hands obscure the wind. Also of note, the Ibike will be upgrading to a wireless cadence as well as polar coded compatability which is important in the peloton.

**EDIT** The I bike is supposed to be very easy to switch between bikes. The polar is not.***
Hope this helps.