The old fan in my '00 XJ is a Dorman 620-001. It came with the car when I bought it used about two months ago, so I have no idea how old the Dorman is. It was working fine, but wanted to make sure the cooling system is in top shape. Before removing the Dorman, I airflow tested it with my anemometer and based on the swept area, I got 780 cfm at 13.3 V. Installed the TYC, and following the same approach, I got 1150 cfm which is just a bit lower than the 1250 CFM rating. So the TYC greatly outflows the Dorman when the fan is running. It could be argued that a new Dorman fan would flow better than my old one, but I doubt it. The Dorman that came in my XJ looks and works 100% fine.
The potential drawback of the TYC is that the swept area is 25% lower than the Dorman, so when the fan is not running, air will not flow through it as easily as the Dorman. This may cause the radiator to be less efficient when driving down the road below the electric fan enable temperature (about 220F). I'll report back after I get a few miles on the TYC.