I fly Airbus's with both IAE and CFM.
Nothing between them really, the IAE's start sequence takes ages compared to the CFM.
IAE's operate on EPR as the main power instrument, but I find most crews still use N1 (as on the CFM).
They both burn roughly the same, both seem very reliable.
The IAE's have a 5 minute warm time (start up to takeoff) restriction that can be a 'gotcha' at small airfields.
We have different on ground ice shedding procedures for the CFM and IAE.
Given a choice I prefer the IAE's, they seem to give a better performance at higher levels (bigger bypass ???).