Calories: MFP or Cardio Machine

Hi friends!

Ive been doing a a lot of cardio lately- mostly elliptical and biking.

However;

when I work out on the elliptical for example, I enter my weight and it calculates calories for me. But when I enter it in MFP its different. The bike is the same way. I will put it on level seven and go for 30 minutes and the machine and MFP (even when I say I was biking with little effort) are completely different.

MFP always says I burn more than the machines say I do.

Which should I listen to? Thanks in advance!