Both are fun (it's skiing, isn't it?
) -- with a couple of limitations. I don't have the patience to SLOWLY ski easy unchallenging stuff for very long, and I'm totally unqualified to help someone else get better (which would make the whole thing more interesting). I'm also old enough and (hopefully) wise enough not to want to put life or limb at serious risk -- I'm not going to follow someone to the gates of hell! Maybe the lack of testosterone has something to do with this?
That said, the most pure FUN I have had skiing are those times when I've been pushed -- because one of the things I love about skiing is pushing myself to ski better, or faster, or on more challenging terrain.
Things change a bit when it comes to group ski lessons, and I think students need to be relatively evenly matched and, depending on group goals, pushed safely by the instructor and each other. The only "bad" lesson I ever had was not due to bad teaching, but to one excrutiatingly slow student in our group. It was absolutely impossible (not just for me but for everyone else) to give this person enough of a head start, or ski slowly enough, to avoid either stopping after every turn or passing her (and our teacher told us at the beginning of the lesson that this was a no-no). This was one of those moments when you thank G-d it's only one lesson out of your life, and not an entire ski week!!!