Comparing Wilson with Sonus Faber is almost like comparing apples and oranges.. both fruit (speakers), but totally different in taste and esthetics. I say this based upon (a) I own SF Il Cremonese; (b) just recently auditioned Liliums and (c) spent 6 hours today listening to Wilson Alexia (driven by the same amps as I have).
Wilson's sound is extremely "detailed", some call it analytical. It is certainly not "warm." They must be positioned particularly carefully and the listener must be very close to exactly in the sweet spot to appreciate their sound stage.SF do need to be positioned properly, but there is more "leeway". I feel that in comparison to SF, Wilson's strength is precision not tonal accuracy. I find that they become "tiring" after several hours.
SF names their speakers after famous violins or the artisans that created the violins. In contrast to Wilson (who strives to have the enclosure contribute absolutely nothing to the sound), SF builds their speakers out of wood and purposely tunes the cabinets to create the tonal qualities associated with a fine violin. (This is definitely not to say SF speakers skimp on other instruments; French horns have their mellow sound, trumpets their brassiness, tuba their grump and you can hear and nearly feels the reeds vibrating in oboes, bassoons and clarinets. The skin of the drum, the resonance of the tympani are clearly discernible.)
I find that the sound of SF is more musical, more engaging and less fatiguing, even when using the same preamp and amp.
I suspect that this impression is dependent on the type of music you prefer (I listen to classical) and I would definitely say that SF speakers are not the best for heavy metal or rock (consider instead Magico, Rockport or perhaps Wilsons).
I personally have found solid state amps to help bring out the best in both brands. At the moment, I use a tube preamp to the solid state amps and find that combination excellent with SF. Today, the Wilsons were powered by SS amp and preamp.
Both are approximately 91 sensitivity so not much power is required.
I strongly urge to hear both, hopefully in a well conditioned room and properly positioned. They really are quite different.
Hope this helps.
PS: I didn't address the appearance: Wilson is industrial; SF is fine furniture. That can make a difference for some.