The March, Chugger, and Blichmann pumps all seem to be produced by the same mfr. The motors look the same to me. The pump heads are different, but they seem to perform similarly. I'm not sure there is a big difference.
I've got a March 815 and it performs well. I do like the features on the Blichmann. I understand that the Blichmann discharge valve can be a little more prone to clogging since its a needle valve style, but if you don't have debris in your flow stream, that shouldn't be a concern.
To give a little background on those mentioned above......
We (March) started making the 809 series pumps back in 1969 for the home hydronics markets....about 10-15yrs ago the solar industry latched onto them as they are rated to 250* so they really like them...that and the fact we do make 12 and 24v versions of them. Some 5-6yrs ago the home brewers starting using our pumps for the same temp reasons. We try and source motors and parts as much as possible from US sources but even US companies are getting stuff made in china and mexico so its getting harder and harder everyday. We do most of the machining here in-house along with plastic molding. The only thing coming from China direct to us here are magnets, as there are very few US sources for those..
The "other guys" used to be one of our distributors...they took one of our 809's to china and had it copied.
Then we think the company they took it to, went and made their own version and the topsflo was born as its the exact same pump head as well just a different motor driver.
Blichmann was picking our brains on their own design...we helped them in some of their testing and we went back and forth on some of their design...but they are basically making their own pump. Its a very nice unit...i'd say it would have been our next generation 809 if we were to ever make a beer only type pump...but they have it covered so we have no interest in it.