Iphone app - Pace or mapmyfitness - pedometer

Hi Everyone

I was hoping for some advice / guidance for iphone pedometer / calorie count apps.

I have used Pacer iphone app as my pedometer for a year now, I saw mapmyfitness in the app's section of MFP and downloaded it. When I ran both apps simultaneously the calorie count was vastly different. The step count was very close though. For a 27 min moderate walk pacer showed 68 calories burnt whereas mapmyfitness showed 127 calories burnt. Given that I am taking one day at a time & would like to be conservative with my calorie lost my instant reaction is to disregard mapmyfitness calorie count . Anyone here has any experience with either or both and can help me ? I am trying to be healthy and count my calorie lost so I can map my food intake better per day.

Thanks in advance