the NGCD is pretty huge inside. Granted there's a lot of empty space, but it's still a pretty large system. I only opened mine once to language mod it (japanese people get to see blood and more bouncy if you get my drift).
these pics should give you an idea of what you'd be in for if you go for an NGCD. oh and the load time *IS* that bad. You can get most of a cigarette in between rounds of KOF99.
an MVS may actually be more compact and less expensive. If you watch ebay for a while you should see some going for as little as ~$50 or so. The MV1-b especially is a farly compact unit and you should be able to 'fold' the boards on eachother (with a very time consuming solder session) to make something very small. Of course you will have to find a screen (like the PSone) that takes RGB in.
here's a couple MV-1B's I picked up, and a picture of what the two internal boards look like layed out:


of course most MVS boards are considerably larger than the MV-1B.