I actually did try out Darius Alpha emulated and I don't get the reason why people like this game. The lasers were all dropping down to the bottom of the screen like they had erectile dysfunction or something. I could get Darius Plus and have the whole game since Alpha is just a boss run.
Where have you ever heard anyone saying they actually like Darius Alpha? Its valuable because its rare. Nobody actually gives two shits about the software since, as you just said, its just a portion of Darius Plus.
I'm going to mention Hanatakdaka here:
I'm not sure how much you're going to actually like it. You sound like one of those guys that just blasts through hundreds of ROMs in an hour, unfarily shitting on most of them, and never taking the time to actually get into them. Nevertheless, this is one of the most underrated PCE games, IMO. I think it costs about $45 or so, usually.