I doesn't matter at all as long as you never get in a crash.
A very valid question that many have asked. Ultimately each of us must decide for ourselves if crash testing and safety certifications have importance or are really worth the extra cost. It is after all, your butt in the bucket.
My thoughts after considering this for a long time:
FIA seat: Actually crash tested design and certified to the highest safety standards for motorsports. Approx. $750+
Stock Porsche seat: Actually crash tested and meets both DOT and EU safety standards.
Non-tested seat: A replica of stock or motorsport design with no crash testing or certification in order to keep costs down. (testing and certification is expensive)
Many disagree but I sleep better knowing my most important safety devices (seat and belts) have been rigorously tested and certified. I have been T-boned and sent into a triple rollover at a controlled intersection where the seat and belts performed as designed and saved my bacon. I do like to save money and my car is pretty frugal in many ways, just not the seats or belts. They are fully tested and certified designs.
We are statistically at far greater risk of collision on public roads than on a race track where everyone is moving in the same direction. Choose wisely for you and yours.