I haven't heard the 2M Black, but I've owned the AT150MLX for over two years. Filmoor's description matches my experience. I find it gratifying that for all the press the Black generated, the 150MLX appears to be in the same league, and possibly better at things that I value (low surface noise, medium output, more textured top end, etc.). I got mine when they were going for $250 for awhile, a crazy bargain. Still a bargain at the current $350-400 compared to the $659 Black, which itself is considered an overachiever. The only thing "wrong" with the AT150MLX is that it's been around for awhile and therefore isn't going to get any professional reviews.
Plus, if it got an honest review it would probably upset the audio press's price/performance hierarchy. I have recently upgraded all cabling from the phono preamp on to the speakers. It has made my system much more transparent and revealing. And one of the things it is revealing is that even at the higher resolution level, the AT150MLX is doing just fine. I have no urge to upgrade there.
Plus, if it got an honest review it would probably upset the audio press's price/performance hierarchy. I have recently upgraded all cabling from the phono preamp on to the speakers. It has made my system much more transparent and revealing. And one of the things it is revealing is that even at the higher resolution level, the AT150MLX is doing just fine. I have no urge to upgrade there.