I have had both, and I traded my SR9c for the M&P9c (I started a different thread about it). In the end, I just liked the feel and ergonomics of the M&P9c better than the Ruger SR9c. Both shoot great, and the trigger on the SR9c is better, but the ergonomics, lack of a mag disconnect/thumb safety on the M&P, and the protruding loaded chamber indicator on the SR9c are why I went with the M&P9c. I also like the flush fitting 12 rd mags on the M&P9c better than the 10 in the SR9c. While the SR9c does have a 17 round mag with extender, I don't see a reason (for my uses) to have that feature...which effectively turns a compact, short barrel gun into a full size handgun. And FWIW, the M&P9c just feels like a higher quality pistol than the Ruger SR9c. Not sure what it is, but it both looks better and feels better in the hand.
That said, the SR9c certainly has features that may be important to some. Personally I don't believe either gun is superior to the other; it is going to come down to personal preference.
In response to the large loaded chamber indicator, I have read some people have solved that "issue" by simply filing it down to a more reasonable level. Whatever works, I guess.
Sig Sauer SP 2022 .40 S&W
Sig Sauer P938