In regards to moustaches:

You keep it well trimmed: You have prickery kisses.
You let it grow to be softer: Your upper lip isn't very visible, but kisses are soft.

So it would seem to me that your wife would be happy to have a choice between the two. That is, if you don't mind growing it out to be softer...

My husband has a full beard and moustache. I like to see his upper lip and don't mind getting pricked! (Go ahead and run with that one, I dare you)

Margarita