You still don't understand
Automotive battery chargers are not designed to do a full charge
They bring the battery to about 90% charge,
They charge enough for you to start the vehicle the battery came out of and to be used intermittently as needed
Power supplies are designed to supply the rated voltage and amps continually, for as long as needed
Most battery chargers will never reach full saturation voltage that will insure the battery electrolyte was returned to correct specfic gravity density
Aka all sulfur from the acid returns to the acid and not left on the battery plates to harden
The mega watt with cables and clamps attached will exceed the performance of any car/vehicle battery charger NOW available
The megawatt will out preform your chosen battery charger
It does require the user to pay attention, it's not idiot proof
Maybe on your case the battery charger is the safer option
And you can upgrade to a megawatt when you have more experience