HSNM is the best I've come across for serious target work, due to the adjustability of nearly every aspect of the pull. With the different springs, it is even more tunable. What sets it apart is being able to adjust each stage weight and sear engagement.
SSA-E and SSA both fill their niches well, too.
The MBT2S is a really good trigger, and for target work I like it as much as the SSA and SSA-E. The flat face doesn't do it for me trying to shoot quickly, but for general bench shooting, I really like it.
I remember the RRA two stage from the days when they lost a stage unpredictably, and just don' like the feel as well the others mentioned. I've shot service rifle with them (most recently shot a loaner one day last year), and while they were fine, they didn't hold a candle to the HSNM.
I shot the KAC/Armalite and CLE/Bushmaster two-stage designs, and while they all had their plusses and minuses, the HSNM is what you see on the line for a reason.