There is nothing wrong with the Prodesign impellers. I have only herd of 2 that had the shaft breaking. It was just probably a year or so ago. It was a fluke thing, and prodesign made it right.
I can garuntee you that there is 100x's more prodesign imellers out there than any other brand.
Modquads have been known to wear where the seal rides, causing coolant to leak. That has been a while ago. I am sure they fixed it.
If I was going to buy one it would be ethire the mull engineering one or the prodesign one.
The mull engineering one has a totally different impeller design that pumps coolant better. The pro design impeller is the Original, all others are just knock off copies.