There is no reason not to buy any of the D5 pumps that are easy to get where you are.
If the pumps are the Vario versions there is no difference at all between them.
If they are PWM versions the only changes made are superficial external PWM mods that Improve the compatibility of the pumps with modern PWM control systems. The first PWM versions of the D5 used a system that produced non standard behaviour of the pump when run without a control signal. Rather than running at full speed like all other PWM fans and devices they would run at the mid range speed of about 3600RPM. They also had some issues working properly with, and being controlled by some PWM fan/pump controllers.
The more recent versions are better pumps for use with PWM fan controllers or modern motherboard fan headers.
I have read some of the comments and threads about modern D5 PWM pumps and just about all of it is incorrect or misguided.
I have been modifying and playing with D5 pumps since before there were PWM and USB controlled versions available.
Last edited by Ashcroft; 06-10-2019 at 12:42 AM.