I already listed them, going from 38mm 360 to 420 isn't going to make a ton of difference for most people. If you're going Threadripper and dumping a crapton of heat with a heavy overclock, this WILL NOT satisfy you. I have used it on a 7900X and while it did OK, the noise ratio of the fans are simply targeted at silence with overhead, such as usage on an 8 core Ryzen.
You could improve the pump or the rad, for instance. Simply enlarging the rad is not much of a different effort than what Alphacool does. Aka not of actual use.
You don't think a 36% increase in surface area is substantial? Not to mention the increase in the volume of air able to be moved by the larger fans?