Hey guys, I know March, and they make some damn fine pumps !
Pump choice is not easy, you have price, size, flow, EM, power use, replacement part costs, looks, etc to think about.
But in my opinion, even though we are some what there competitor (not really given low PC liquid cooling numbers), that you should feel secure with one of there brushless units.
Don't worry about them only rating the motor, there are SO MANY factors effecting pump life that it's almost impossible to predict for every application.
"March has an impeller spinning on a shaft
C-Systems has a steel shaft with a seal
- both weak links if going for 5 yrs service"
Sorry Bill, but must say something about this.
First your right, both designs can fail. But a good designer considers there will be failures and what to do about it. Assuming even a Laing unit will not ever fail is wrong.
One answer is monitoring, and low cost replacement parts. With AC pumps you have this now, as the impeller will make noise and a replacement is cheap. Not sure what cost of impeller is for the March unit, but would be nice if low.
But the "ideal" solution is mag coupling, impeller speed monitoring, low costs, small size, cheap replacement parts, long lasting in fluid bearings,and low EM / power use /noise.
But that pump does not exsist, and likley never will, well maybe with future superconductors