Seasonic are using a Hong Hua 135mm fan, Model number HA13525M12F-Z. This is the exact same fan fitted in the 750W and 850W PRIME units.
This is a Fluid Dynamic Bearing Fan selected for low noise characteristics. Regular readers may recall that the Seasonic Snow Silent 750W unit shipped with a smaller 120mm fan from the same company so its interesting, and likely a good move that Seasonic are adopting larger fans. Larger fans of similar quality are able to push more air at the same speeds, likely often spinning slower to reduce noise emissions.
The soldering quality throughout is top drawer and it is clear that Seasonic have succeeded in reducing system clutter thanks to their new internal cable free connection design. There is a copper plate connecting the back panel to the main PCB to increase reliability and improve performance. They are increasing their use of paste solder throughout the design for quality reasons.
Seasonic are offering a full 10 year warranty with these power supplies so it is clear they are confident of long term reliability and stability.
The Prime supply adopts high grade Japanese capacitors throughout both primary and secondary stages. The primary stage is served by two 105c Nippon Chemi Con capacitors rated at 400v 450uF each (for a combined total of 900uF).
The 750W Prime is served by two 105c Nippon Chemi Con capacitors rated at 400v 560uF and 400v 450uF (for a combined total of 1010uF). The 850W Prime is served by two 105c Nippon Chemi Con capacitors rated at 400v 650uF and 400v 450uF (for a combined total of 1100uF).