When do you prefer a character's appearance to be revealed?

I like both techniques you wrote, to be honest. When I read I like to be told almost immediately what the character looks like, but I absolutely hate it when the author stops and thinks that's enough. As if they think the reader won't need a memory refresher. So, as I read on, I like it when the author slips in little details throughout the story. I think Rick Riordan does a great job of doing this and I'd look into a couple of his books.