Polar Calories Burnt vs. MFP

I bike to keep lose weight and it is working. I just did 1h 47m of biking, averaging 13 mph. MFP states around 1100 calories burnt, where as my Polar app (with heart rate monitor sensor on my chest) states 1600. Averaged 160 bpm with a high of 182.

Does anyone have thoughts on accuracy here?

I am losing weight- smarter eating + tracking cals w/ MFP and being active. No complaints, just wondering about the calorie disparity.