As one way of judging, inquire regarding the construction of the impeller. It's common to have a stamped steel impeller in run-of-the-mill pieces, and a carefully designed cast piece in the quality pumps. When Ebock first offered aluminum FE pumps they used stamped steel, and had a rash of early complaints. When Dove decided to build water pumps he did a design analysis of the impeller from Ford designed to go in the road-racing pump for the Boss 302. He took the design and scaled it to go in the FE article. Worked great.
KS