are they more expensive? are they as good as the super8's?
Yes they are more expensive (new at least).
They are MUCH better than the supers. I have replaced supers with Wico leafs many, many times.
I would actually shy away from "new" Wico leaf joys, since there is apparently a repro out now that is not as good as the originals. Just stick to used ones. Used ones are very easy to find, they are on ebay all the time. You can often find a complete control panel with a pair of them along with some leaf buttons at a very cheap price.
Also, leaf buttons seem to still be in production, and are easy to find.
Leaf controls get a bad rap only because people hear rumors about having to adjust them. Yes, in 1982 when games got played 12 hours a day, yes you would have to adjust your leaf switches about once every 6 months to a year, and if an operator owned 200 games, that made it seem like he was doing it everyday.
In the reality world of home use you will likely adjust your leaf switches upon installing them (or bringing home a new leaf game, or pin, pins have TONS of leaf switches), and then never have to adjust them again. I have been collecting for almost 4 years now, and I have never had to adjust the same leaf switch twice.