Ignoring the actual characters for a moment, I prefer beards. Mustaches tend to make you look like a pervert or a 70's porn star or a pedophile, beards tend to make you look awesome. Unless the mustache is attached to a beard as part of a set, then it's okay. But a mustache alone is not acceptable.
It's this simple math formula:
beard=awesome
mustache=horrible
mustache+beard=awesome
...Unless you're Mario (the Nintendo character), because he somehow pulls off having a mustache without it looking bad. I don't know how he does it. If you're wondering, Dorian's specific look of having a mustache makes him look like the "70's porn star" variant.