"In the last few months, Boeing’s re-engined 737 MAX has quietly run into a bit of trouble. For weeks, sources at the Melun-based engine manufacturer CFM have quietly noted that the LEAP-1B engine that will power the 737 MAX is facing a serious performance shortfall of close to 4-5% in specific fuel consumption (sfc), and the LEAP-1A–that will power some of rival Airbus’ A320neo aircraft–is facing a smaller 2% sfc deficit."

I should have been more clear that I was talking about the NEO and MAX CFM engine. Above is quoted from an article I found and prior articles talked about the smaller fan size on the B737 MAX because of the ground clearance. So the Airbus has a larger fan diameter with the same engine and will burn less fuel. I just took the 5% and 2% difference, in the above quote, to come up with the 3% more fuel burn.