Each would charge your battery. If that is all you want the generator to do, I would go with the quietest machine.
The EM500 is a 500 watt model, flathead-style 60cc engine with a cast-iron cylinder sleeve. It runs at full throttle when making power, regardless of the load. Last made in the early 80s, parts are getting more scarce, but still available. Here's a link to an owner's manual:i have found two Honda EM 500"s that run well for $200.00 and the other for $250.00 with the 12 volt charging cord...and a Honda eu1000i