I have one (Japanese MVS) and I swear by it. The systems is:
(A) easier to open up and get inside to fix and replace carts (everything opens in the front!)
(B) They almost always have wheels on the back so you can move them easier.
(C) THE MONITOR! They generally have much larger monitors than their American bretheren.
(D) they're not very small! While they're shorter (You have to sit on a chair or stool), the large monitor makes them a bit longer than the US versions.
The Japanese are serious about video games (if you've ever been to a SE Asian style arcade in the states, you know what I'm talking about). They designed these systems to be easy to operate, efficient in size, and kick ass. I have two Japanese cabnits: a dedicated MVS and a Sega AeroCity (its a generic unit for Jamma boards). I bought each for $225 (roughly). I also have a regular American cabnit for Time Soldiers, but it's a unruly behemoth compared to the other two. There's no comparing!
Hope that helps
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Bobak!
You can also see me in the classic SNK game, "Guerrilla War" (known in Japan as "Guevara")