In theory the lower level signal from the pre-amp is more susceptible to loss and noise, and then that noise will be amplified. The high power signal going to the speakers is quite robust, as long as you use a sufficient gauge of properly designed wire. So it would make sense to keep the interconnect cables as short as possible and go with longer speaker wire.
In practice, as long as you're not talking about 100s of feet it doesn't matter either way. The amount of wire involved just isn't enough to cause any trouble with well designed products.
Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs