360 MBL is pretty accurate overall, so it's the one I play now. Arcade mode has more slowdown in the stages, but less on the bosses and (especially) the Ice Palace.
I like the look of DSII, I just want a port with the same slowdown as the Arcade Ver. Since it was coded on a Windows PC, basically, it should be the easiest port ever to make 100% accurate, if we could just find a company that cared enough to do it. I remember CAVE said they did the X360 port of the Arcade DSII in about 3-4 days. Just slapped together at the last minute, super buggy and no care taken to tweak the slowdown accuracy. A real shame.