I had issues with both the MAS supergun and the HGA supergun.
MAS has better joysticks, but I had problems with the RGB converter and my 1-slot (no picture). He wanted me to modify my 1-slot, and to me that was a red flag. I have heard that others have blown expensive TV's (Sony WEGA) with the MAS converter.
The HGA system is generally fine, except the quality of the joysticks is not to MAS caliber. The picture was a problem though (I had the S-Video connection). Everytime the action on screen got intense the picture would break up. This ruined the quality of the overall experience to the point that I almost completely got out of the Neo scene. I did however buy a cabinet and I am happy with that (real arcade experience).
I am planning on building my own supergun, but I am researching it dilligently first.
Their is a product out of Japan called the Vega Jr. that NCS is trying to find for me, that looks like a good unit (I posted a link of the picture somewhere here).
If !Arcade! comes through with the AES 2, it would be the greatest boon to the Neo Community since, well since they started !
Their contribution would be so big it would help keep the Neo alive for another 10 - 20 years. These guys have the capability. And the unit if it contains all the functionality that NeoLord called out previously, might be somewhat pricey, so what, it would be worth it, and I would probably buy two.
Maybe E3 will shed some light on all this ???
I probably didn't help you, just wanted to let you know what I have run into in my Neo gaming experience.
Good luck with your decision...
searchingtom