I had started a thread about IAE and CFM engines I had observed following shortcomings of IAE engines:
CFM VS IAE Engines A320
IAE engine takes longer to start than CFM. Also thrust response to thrust levers appears sluggish as compared to CFM.
IAE engine as you open thrust for take off appears bit noisier than CFM.
IAE has fan flutter that is why there is KEEP OUT ZONE between certain RPM when applying take off thrust while there is no such thing in CFM. IAE requires or puts on ignition for more conditions than CFM.
IAE engine for circling approach OEI and flap3 is seven tons more weight restricted than CFM for circling.
IAE engine aircraft have Flap full with flaps at 40 while CFM engine aircraft have flap full with flaps at 35. I don't know is it because engines size or shape.