I have both the SR9 and the Security 9.
I am an avid supporter of the SR9, probably too much so. It is hands down one of my favorite striker fired pistols. It points well, shoots well, feels good in hand, etc. etc. I dont care about the additional safety features that are a bit 'annoying'
That said, the security 9 is a fine gun. I've put thousands of rounds through it. I had a minor extractor issues after about 2k rounds every 3rd magazine or so was having an FTE, so I sent it back, put another 1k through it no issues so far. Ruger being Ruger not only replaced the extractor, but the barrel, guide rod, slide as well.
I agree with Carl as I have in the past the the SR9 is a better built weapon. But I also think the Security 9 has its place and I wouldn't hesitate to buy another.