Polar or fitbit force/flex?

I have a Polar FT4 and I LOVE it. I've had it for 8 months now and it still works great.

Also interested in the answers here, please keep them coming.

Since I've spent so much time reading different reviews and doing research recently, I'll share the best of what I've found.

A Fitbit is more of a device to keep you motivated and on track, rather than an accurate calorie counter. The newly released Fitbit Force is supposedly much more accurate than the Flex when it comes to monitoring movement, but that's just what they do. They count your steps and monitor movement to estimate your calorie burn http://bit.ly/1gggOwn They don't measure your heart rate, which means there are some activities in which the measurement will be totally inaccurate; ie cycling. With your hands being stationary on the handlebars, these devices will not be able to accurately track your cadence and may have no idea how hard you're working. That being said, if you're still looking for a wearable, you may want to look at something like the Basis Smartwatch http://bit.ly/18IrvPy It has a HRM, but there still aren't any HRM's which you can wear on your wrist which will accurately measure high intensity activity. The technology isn't there yet. It doesn't sync with MFP yet though which may be a deal breaker for you.

If you don't need a wearable to keep you motivated, then simply figuring out your average BMR through trial and error should be enough for your living/resting energy expenditure and a real HRM like a polar would be the way to go to measure actual workouts. I recently purchased a Polar FT7 which I've found to be accurate.

Keep in mind, when using a HRM for workouts, if you want your log to be very accurate, you need to subtract your living calories before you log your workout expenditure. For example, let's say your BMR is 2000 and you weigh 100 pounds. To calculate your sleeping BMR, use a number like .4 calories per pound per hour of sleep. If you sleep 5 hours on average, .4 x 100 lbs = 40 cal per hr x 5 hrs sleep = 200 cals. Then take the remaing 1800 cals and divide them over the 19 hours you usually spend awake. Call it 95 cal per hr. If you do an hour workout, subtract 95 cal from your HRM #. Why? If you didn't workout at all, you would have burned about 95 cal anyway and that's already factored into your MFP BMR. Of course there's no perfect science for calorie counting, but this is as close as you can get.