Welcome to TFL
I think you made a great choice! I've owned both, still own the MP9c
Both are great guns. What I couldn't get used to on the Ruger SR9c was the fact that there is essentially no slide release. There is a slide "lock" but you still have to use your weak hand to drop the slide on a new mag. It makes no sense!
Also, as MLeake said... the ergos are much better on the M&P. All the fuss about the M&P trigger is overrated. It's not that bad... and it's an easy fix. I'm not a fan of external safeties either, so that's a plus on the M&P9c.
Again, both are great guns. IMHO the M&P9c is a step up from the