Apologies, I might have jumped the gun then.
I agree with Lord Cavash, it comes down to personal preference. Some archons might prefer the Sslyth, their sheer tenacity and esoterism can be quite the boon, espeically against upstart mon-keigh. On the other hand, the armaments of the incubi are very fine, and they are one of the two things you can trust in the dark city (the other being that Vect's will is absolute).
I myself prefer incubi, as not only are they very fine bodyguards, but they are a most joyous sight to behold on a raid in all their action. They also serve as a nice filter to allow only particular champions of the enemy to close in.