I played it on my Sega CD back in the day.
It's still reduced from the "portfolio game" (not really a board game either) in that they simply couldn't portray every location in London like the Directory/Encounter Books do and you also don't get as rich of a newspaper to scour through.
I believe the cases still solved the same, though. But the acting wasn't exactly spectacular and I think a good part of the fun is being with friends poring over the map and the phone directory and the newspaper coming up with theories.
I also don't recall there being a digital version of The Mansion Murders, but I could be wrong there.
That was very helpful, thanks! Yeah, I've noticed that the acting is pretty bad... But I had hopes that the electronic version would be closer to the original than what it sounds like.