I practice aerobatics at 6000 in Extra 300.
It gets there quickly & gives me plenty of room to sort out.. errm unsual attitudes.
Also. I've got no heater! So going any higher I'd be freezing my balls off. Nobody wants that.
For cruising, 4000-5000 seems to be a nice block of altitude for me. Not too cold and I can easily transition across most airspace. Descent doesnt take forever & I seem to be above most of the slower GA traffic just because they dont want to waste their whole trip climbing but I still tend to be underneath the turboprops and the likes of on longer trips.
It varies from place to place. - Also the extra glides like a brick, so I need the height if I lose an engine.