Polar Loop or Polar or ft7?

It depends on what info you desire, as well as what your goals are. Both have advantages and disadvantages.

I have the FT7. Love it. However, it does not sync with iPhone 4, or MFP. you must manually enter the cal bum. I use the Polar website to figure cal burn, then enter into MFP. However, I now have my eye on one of the polar HRM that sync thru blue tooth to the iPhone 5. You can get the FT7 to sync with polar if you buy the dongle thing. your choice. I have used my riding bike, walking, running, and swimming. Swimming in highly chlorinated pools messes with the transmittal of data to the wrist part and can alter your average HR reading. Some models aimed at swimmers/ triathletes do not seem to have this issue. the FT7 is a good overall, entry level HRM. It does not have lap times. I suggest going to Polar website and using the cute tool to help pick your best model. Timex Iron man, Garmin, and Tom Tom also have HRM you might look at. Best model for you depends on what you need it for and cost. I strongly suggest one you can replace the battery on yourself and not have to send it back to company for,..

No matter what device you have, you need to enter your weight, height, gender.