In general Mansfield Products don't get much love on this list. For the Professional I completely understand the TOTO preference. For the DIY Plumber a step up from the builder grade Mansfield Alto is worth a look. The Summit 3 is an offshoot of the Maverick and owes its utility to the flattery it gives the Drake employing the 3" flapper and the 2-1/8" glazed trapway.
Have a look, good performance 600Map...
BTW the Maverick is imported and the Summit 3 is made in Mansfield Ohio USA!