We operate A319s/A320s with the CFM-Engine and A321s with the IAE-Engine.
As a driver, I'd prefer the CFM any day. The problems have already been named, the greatest disadvantage ist the mickey-mouse-style thrust indication on the IAE.
If you have a grossweight (landing weight) of lets say 58 tonns on a CFM-A/C, you would set N1 to GW-3 as a thrust target xx% N1 during approach, in this case some 55% N1.
On the IAE your target ist 1.0xx EPR and already by looking sharply at the trust levers you change EPR easily by > 0,01-0,02. So good luck in a heavy A321 (greetings from the slow reacting engines) on a windy day.
Also the EPR display on the IAE-A/C is a good bit smaller behind the decimal (compared to the N1-Display on the CFM-A/C), so looking at it to read the EPR takes always just this 'microsecond' longer, in which you should have been looking at the intruments/outside.