Both are a solid choice no real problems with either. do you prefer striker or hammer that is the question. my advice is get both then buy a glock,hk,sig etc..
I've never had FNS but had an FNP9mm and think quality it was better than MP
Just bought my first pistol, and my experience was the exact opposite of this, although the M&P has way more support, I handled and shot both, and I found the FNS to be a much nicer and at least to me, a way better built pistol, I thought the M&P felt cheaply made by comparison, I guess everybody has to choose what feels good to them, in my case, I bought the FN, to me it felt like a much nicer pistol, especially for the cost, simply couldn't justify $250 more for what I felt was a lesser gunThe M&p has far more aftermarket support, parts replacements, barrels, holsters, mags are easy to come by. The M&p feels less cheap in hand, you feel like your holding something they actually took some time to make and design. not to say the fn is garbage it's not, it just looks and feels very plain