MS3 IGN hands on-
http://xbox.ign.com/articles/509/509...html?fromint=1
"Though MS 3 is similar to the arcade, there are a few good additions. For one thing, there are two extra modes (Storming the Mother Ship and Fat Island) unlocked when you beat Arcade Mode, and there are no quarters required to play (just $40 for the game). However, where you could plunk in a quarter or two to continue from the spot you croaked in the arcade, for the Xbox version continues take you back to the start of the level. The value of the continue is that it continues your score tally. This makes things a bit tougher, but extends Arcade Mode a bit, since it will take a little longer to beat."
"The arcade version of Metal Slug 3 isn't quite as pretty as the Xbox version, which offers sharper visuals and better contrast between the 2D sprite characters and the attractive hand-drawn backgrounds. The slowdown, which plagues many of the arcade Slugs, is pretty much non-existent on Xbox. It sounds small, but it makes a big difference in the overall experience and even in control, because there are scores of enemies coming at you at all times so a smooth framerate helps towards victory. Though the graphics might not be as stunning as everyone's used to on Xbox, this is a very colorful game with a distinct artistic style that helps it stand out."