South Korean or German Dermaroller,Stainless Steel or Titanium Needles, Which is Better ?

The following questions will surely help people that want to know more about the dermaroller procedure. So please contribute. 1. It is touted that the German contructed dermaroller is better than a South Korean(Dr-Roller brand) dermaroller, is this true ? 2. Confusion exists,because marketers for some dermaroller brands claim, that needles made from "surgical grade stainless steel", is better than titanium made needles, and vice versa. Which is really better, stainless steel or titanium ?