Exercise tracker

Delldgm

Hi everyone
So a question about tracking your exercise. I have been using a phone app called noom that tracks time, distance and calories with GPS of my walking, it's cal burnt is different than just putting in the exercise into mfp. But then I notice that mfp has an app to do the same that can synch to mfp automatically. So on my walk today I used both,( now don't laugh that I track so little an exercise but its all I get done at the moment so I track it to start good habits) but one noom came in at 59 cals and and runtastic (the mfp app) came in at 159 cals which one should I use?

Thanks
Dell