Check this article comparing both TSMC and Samsung A9 chip which I think is the fairest and non bias out of all publish articles, it's actually quite similar and even better than TSMC, anyway don't feel sad if yours is build by Samsung, the difference is not that much, it's overhyped by media. The setting, the apps installed, the background apps, brightness all affect each device during the test. So just enjoy your dear iPhone 6s series.
All different testing show it's quite similar results except Geekbech that show huge difference like 20% in result, so who knows, maybe is something is not working right with Geekbench itself. With iOS 9.1 coming very soon in two weeks time, it will be even optimized so sit back, relax and enjoy the phone, and stop the never ending "gate" stuff. Haha!
http://www.tomshardware.com/news/iphone-6s-a9-samsung-vs-tsmc,30306.html