Depends on what you are doing!
DOS will run MAME with a suitable frontend(ArcadeOS) for output on an Arcade Screen.
Win98 will run fine with a suitable Video card on a SVGA (Normal Monitor) or on a TV (With TV out).
It can also be configured to run faster, programmes like
x-setup will allow you to tweak various settings.
I ran a program called 98Lite which removed Internet Explorer (I didn't need it) and replaced the regular Windows explorer with the Win95 explorer (Speeds up the system!)
I think I'm going to put windowsME on my new cab, and I'll see how this works out. I run Win2000Pro in work but really don't see any need for running this in a Cabinet.
On RAM - again depends what you're running (The more the better!) But aim for at least 128Mb!
