A truly plain pizza is focaccia. What we usually call "plain" is topped lightly with sauce and cheese. It is better called what it is, cheese pizza, typically thought of as New York style with a thin, flexible crust.
That is a semantic position, though, and I don't want to be pedantic. I think I know what you mean in asking the question: do I prefer light cheese pizza, or do I like to add additional things to it? The answer is that if I want a slice of it to fold up and eat while walking around, I want it simple, with nothing else on it, so I won't spill things all over my clothes. If I'm having it sitting down, I want a heavier version of a pizza pie, so I load it up with whatever seems good at the time.