Masks, prosthetics, and makeup all have their place. Our shows use a pretty even mixture of them all. Also, I tend to enjoy shows a little less when they don't have a variety of characters, i.e., the actors are all wearing masks or are all painted the same way.
Personally, I like wearing a mask far more than prosthetics. My mask doesn't fall off or peel at the edges when I'm sweating buckets from running nonstop for hours in the Texas September heat.