I'm just getting started here, so my experience is very limited. I am fortunate I have both SASS and an NCOWS posse within 20 minutes of me, so I joined both and am playing at both ranges. I will say, what I like about NCOWS, is the shooting. I love, that there is a focus both on time, AND accuracy. I don't know how other SASS locations do it, but our local SASS matches targets are closer than I have ever shot at anything ever, and the focus is on SPEED SPEED SPEED. That's all well and good, but I personally am not a fan of blowing through 10 rifle, 10 pistol and 4 shot shells per stage, at that close range. It's all a time thing, very little shooting skill involved, just muscle memory to get rounds off fast.
My local NCOWS is timed of course, but with targets set at realistic distances, some rife out to almost 90 yards, you have to actually aim, and display some shooting discipline. This, I LOVE about NCOWS. I'm also a fan of the simplicity, and lower round count per match. With 3 matches a month between the two I will probably shoot both for a while, but I'm very heavily leaning toward focusing on NCOWS for sure. And, of course? The people! (and this does go for both....great people in the sport, helpful, friendly, and just plain fun). Good stuff!