Endomondo vs MFP

I downloaded Endomondo on my phone to track my walks/jobs. This morning I went for a walk on my break (11 min) and Endomondo says I burned 91 calories and when I put the info into MFP it says I only burned 55. I am going to go with the 55 cuz I don't want to overestimate but can anyone explain why the difference?
Thanks!!

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