I can't ever remember reading about someone praising the HGA system. I have seen this topic come up quite often and the Super Nova wins hands down according to public opinion.
From my expierience,the MAS stuff is really nice but not as durable as it once was back in the early 90's.
If you are a NOVICE in MVS gaming and just want to enjoy Neo Geo exclusively I would have to recommend that you purchase a NGH System and the latest revision of the Phantom-1 MVS cartridge adapter by !ARCADE!
You probably want to delve into Jamma board collecting as well so the MAS Super NOVA would be ideal.
-BB