The Amarine unit is a stripped down pump. Among the missing items are that control switch, storage box, and not sure it is a positive displacement pump (just a centrifugal pump which may run out of steam with higher lifts). Also no flush fitting to help "jet out" any stubborn residue from the black tank.
There is also the "Recpro" macerator pump that is a knock off of the Flojet but most knock off's usually are built as cheap as possible. How else can they keep the price down.
The Flowjet has thermal protection so if it heats up from use the motor won't destroy itself. Let it cool and back in business (of getting rid of your business
Flojet has almost 1200 reviews on amazon. As I read through many of the negative reviews it is apparent that operator error of basic knowledge of electric/mechanical devices was lacking. Just check to see if motor runs freely before trying to pump sewage, being careful to not break lock tabs off when attaching, and not running forever or through a small hose can go a long way toward eliminating those issues.
I don't sell Flojet pumps but have had my fill of cheap knockoffs so I don't buy on the basis of price. But that's just me.