I love joe, but I'm sure I would be fine with vi if I'd learned it (well) first. I use joe because it's small, fast, functional, and easy to use. On that scale,
joe > vi (not easy to use) > pico (not functional) > emacs (not small, fast, or easy to use)
I would have assumed most joe users felt the same. If I don't have joe, I use vi. I'd never dream of installing emacs or pico on a system I couldn't install joe on for some reason.