I've seen kits with both of these pumps and my instinct is to go for the one with the deeper impeller fins, but I don't know if my thinking is sound. Also wonder if certain engine specs call for one or other of the pumps. If not engine specific then why the two types?New water pump and old water pump side by side, the new one came as part of a gates cambelt kit with a new tensioner.
Now which one do we think will move more water and also which one do we think would be a better quality and more expensive
Another factor is that one is a metal impeller whilst the other is plastic. There have been problems in the past with plastic impellers coming loose from their spindle - and so not pumping properly. It's quite difficult to diagnose why an engine is overheating due to a loose impeller as there are really no external clues like "grumbly" bearings etc - However I've not come across a loose plastic impeller for some time so maybe they've pretty much sorted that problem now?