My guess is that using heavy naphtha is preferred. The combined liquid and gas should not go through a dry point inside the compressor meaning that there should be some liquid in the fluid as it leaves the compressor. A higher boiling fraction will result in a two phase flow on the compressor discharge. A lighter naphtha would require more liquid be added to prevent a dry point in the compressor.
A dry point would result in deposition of material on the compressor impellers and then no liquid to mitigate the increase in temperature due to compression. There will be more dienes due to the liquid injection and the probability of polymerization is higher than if no naphtha injection was done in the first place.
I think either could be used, but enough naphtha has to be injected to prevent a dry point in the compressor.