If I were buying one right now, I'd probably jump on the springfield, just to see. I like the features. I'm with what the other guy said, FSB's aren't a bad thing, but I do shoot irons a lot. And the Saint's longer sight radius would be good. Plus I think the fact that they put a decent trigger in is a really good idea. Some factory triggers can be pretty darned heavy. They also have a really good warranty policy.
But yeah, you can't go wrong with a 6920. And really all of them are probably serviceable. The 6920 is probably the one that you could trust the most on reputation. But even with that you have to run some ammo through any gun to see how it's going to perform.
Having said all that, I think the most popular type of set up with a lot of the in the know dudes is a 16" mid length medium weight or even LW barrel, with a decently long and light rail. Slap some magpul buis, a quality RDS and a light. Or now a 1-4 instead of the RDS. And there really isn't a better do it all set up for a carbine. Until you get into SBR's with cans.
Mids will usually have a bit less recoil than a carbine (like the 6920) and follow up shots are quicker. The longer rail gives you more real estate for a good grip, and a light, and sight radius for irons if you're going to use them.
This is the 3rd time I've posted this vid today, LOL.
patscarbine