I first learned on an artificial slope in Sheffield (a long, long time ago), and there's now an indoor slope (with "real" snow) about 20 miles from where I live.
The artificial stuff is really painful if you fall on it, and I ruined about 5 pairs of pants and a number of jerseys on the stuff (not to mention the foot long abrasions on my hips and shoulders) before I learned to ski on it properly
. Snow is a lot easier. The only trouble with the indoor slopes is they're usually too short and too shallow to have any real fun on them, but they are a good training resource for beginners, and a useful place to practice technique if you haven't had planks on your feet for a while.
The artificial stuff is really painful if you fall on it, and I ruined about 5 pairs of pants and a number of jerseys on the stuff (not to mention the foot long abrasions on my hips and shoulders) before I learned to ski on it properly