I think it depends on what you're going for, and your level of proficiency, and your situation, honestly.
A party situation, where you're going to be talking, eating, etc, a mask can get inconvenient in a hurry, for instance.
Sorry for the crappy pic, cell phones weren't what they are today back then, here's a friend of mine I did up as Hellboy for a party. Sculpted, cast, applied those horns
Yeah, the hair work is not the best, yeah the paint job could have used more time, but 30 minutes applied and out the door is not too shabby.
Small things can be easily applied with makeup, too.
My son on the right there, his first year "working" in the haunt, wanted to be a headhunter (which since our yard was afew hundred skulls on poles at the time made sense). Glueing on some bamboo kabobs to look like he'd been pierced was a simple matter.
Simple flesh peeling is deceptively quick and easy with a little liquid latex as well. (forgive the green it's all I had when I did this. one handed, teaching a group of kids/soccer moms some real basics)
All that said, if you got several folks you need to get ready, masks are definitely a good option, and my typical go-to now that I'm trying to get 3 kids and myself ready in a reasonable amount of time.
HAVE to share it 
