Both games lend on WMS "Flash" pretty heavily. Skateball is Drop Target Heaven and has a mini flipper up the top for the 3 DT Bank. Great fun to play and fast gameplay. As with all Bally's from this era, the artwork is awesome. Fairly easy rules to follow, so it does not take too long before some serious high scoring can be done. Not a multiball game. It does have lasting appeal.
Fathom is simply one of Bally's finest moments. A progression from Skateball with the addition of "in line" Drop Targets and memory recall on the targets. So it is a complicated game from a technical design perspective. Rather than one bonus system, it has two. One "green" and one "blue" - so you have two bonus countdowns. The saucers behind the 3 Drop Targets capture two balls and then you knock down the DT's for that ball to be released. It is fast, unforgiving and one of the best playing games of all time. The artwork is in the top 5 art packages for any era.
Skateball could be considered the poorer cousin of Fathom. If you want similar gameplay to Fathom, but you cannot source the game or you don't want to pay over $4000 for a good one, then Skateball is a cheaper alternative.
Both games borrow heavily from Flash, but Flash has a Bally connection with some similarities to 4 Million B.C.
