Should I buy the MSI 2070 Super Gaming X (Trio) or Nvidia 2070 Super? Its so much cheaper to buy the normal one by Nvidia, and I wonder if its worth buying an expensive custom card by MSI, Asus or Gigabyte. Whats the difference in performance?
Performance difference is very small to even consider it. The main difference is the custom PCB (which also may include different power delivery), the cooling solution, the aesthetics and the size.
Personally I buy from brands to have better cooling. That helps when you want to OC and even if you don't, the card boosts higher(GPU Boost 3.0) since it remains cooler.