The reason:
There are three main NAT types depending on your platform: Open, Moderate, and Strict on Microsoft or PC, and Type 1, Type 2, and Type 3 on Sony. Moderate/Type 2 and Strict/Type 3 NAT types limit the connections your gaming console or PC can make to other gaming consoles or PCs. For example, Moderate/Type 2 NATs can only connect with gaming consoles or PCs using Moderate/Type 2 or Open/Type 1 NAT, and Strict/Type 3 NATs can only connect with gaming consoles or PCs using Open/Type 1 NAT. Ultimately, an Open/Type 1 NAT will provide the best connection quality.