A pump is depending on your hardware.
What CPU block do you have? One of the restricting kind (White water) or one for more flow? (Maze 4 e.g.) the same goes if you have more blocks for GPU and Northbridge.
What Radiator do you have? They come in all types and shapes, restrictive and not so restrictive.
Depending on your setup, both the MCP600 and the Eheim are a good choice.
If you look at
this Article , you know why.
The MCP outperforms the Eheim a bit in almost every setup. It’s smaller, quieter and uses less power. (I must look like a commercial) but a bit more expensive.
If you have a “non restrictive” setup, the Eheim will do just fine also.
If you have a very restrictive setup, you might even want to use 2 pumps.
Depending on the availability and price of the pumps, you should make your choice.