Never owned one, but it seems to me like Chicago Gaming Company (CGC) is upping their game with each new pin they release. I think everyone can agree that their first machine (Vacation) was hot garbage. Each remake they have made (Medieval Madness Remake (MMr), Attack From Mars Remake (AFMr), and Monster Mash Remake (MMr) seems to be adding more features. The base of each seems to be about the same, but the Special and LE seems to be piling things on. I think the MMr topper is still the best topper I've seen, but Monster Bash has those cool color changing LEDs and the cool plasma disk in the back. I don't think AFMr really added anything (other than the topper) and some extra color changes in the UFOs. I forgot to mention how awesome the SE and LEs sound and the cool full color XL DMDs.
I'm stuck with an old WCS but some day... I think I'm going to do the upgrade to a new machine that doesn't require a repair every other week. Monster Bash seems nicer than the other ones at every level (except the topper) but I still think AFMr is the better game.