VorTech mp20 or mp40?

[spiderwoman]

I'm going to upgrade my ph's in our 75g reef to VorTech pump. MP20 is for tanks 20-70 and could work by itself for the 75, but MP40W would be something that I'll never need to change for the tank. I have Tunze's in the 150g reef, but wanted to try something different with this reef.
Which would you go with? Aside the price difference, just thinking about the amount of flow.

 

[spiderwoman]

Forgot to say that currently I'm running 2 #4 Koralia's and a #3 Koralia on the tank and I'm sick and tired of the #3 dropping it's cover at least once a week. It just does NOT stay put.

 

[rebelprettyboy]

the MP40
and a K4