I have both machines, and the above responses pretty much summarise the gameplay. Both rank highly for me, as this era of pins (late 70's/early 80's) and Ballys is amongst the best.
Skateball was THE first pin I purchased, and was restored by Nino along its past. I actually have completed the restoration of the cabinet some months ago (respray), and will get around to a resto thread on that someday soon. With an exceptionally good BG and day one mylared PF, it's very nice all around.
Skateball is a title you don't see come up much at all.
Fathom, as Nino has covered already, is an amazing and very unique package of art, sounds, and gameplay. But since you own one no need really for me to say any more on it.
Hope you find a Skateball one day - it's one I think worth having in the collection (at least for a while).
