Nenuphar's are a more "complete" sounding speaker for me.
Does things like coherency and portray realism better.
Better integration of low/mid/high's compared to IQ. (Nenuphar mini's are better than Neuphar's in this regard)
However, the amplification matching is totally different between the two.
Nenuphar's are harder/more demanding to match and they reveal changes in upstream gear much more than the IQ. (no crossovers)
IQ's are much more forgiving with amplification... they generally like high current/fast amps.
For most ppl, I'd recommend IQ.
For obsessive tweakers who like to tinker and get into various tube amplification, Nenuphar's might be your cup of tea (no one "right" amp, every amp/tube has their strengths and weaknesses so you have to match according to your preference)