It all depends on the machine. For example lets look at Ranma 1/2. The anime series never showed the last few chapters of the manga and about the only way to see the resolution in anime form is by playing pachinko. Watch this video:Morti said:So... it's not really continuing the story with the machine, it's a poorly animated pay-per-view cut scene that happens to be on the machine?Blazing Hero said:Most modern day pachinko machines are hooked up to lcd monitors which play out stories while you score points. A lot of preexisting manga and games only continue their timelines on these machines. For example the Ranma pachinko machine basically plays the last few chapters of the manga that never got animated and provides the actual ending to the anime. The same is true with Evangelion where the story is continued across Pachinko Machines only while you play. So if you want to see the story continue you are stuck having to gamble tons of money on 9 separate machines with a new one being released practically every year.
Now getting back to Silent Hill, the pachinko machine is going to be based on Silent Hill 2 so it would be expected in Japan that there would be new scenes and situations added to that story. But be aware that usually what is added is god awful. To give you an example of what to expect check out some of these scenes Capcom put in the original Resident Evil Pachislo machine. Its actually pretty damn funny,
https://www.youtube.com/watch?v=3CgbQnI_oeA
Edit:
Here's another one just for fun
https://www.youtube.com/watch?v=oBRtkccCXms
https://www.youtube.com/watch?v=4wFBPfjihAk
As you can see it isn't really that cutscene based but more along the lines of watching a full anime episode. Unfortunately it is random and varies from machine to machine.