It depends upon what you want to use the EX650 for and where you want to use it.
With an EX650 powering the right 30 amp multi-stage charger, the EX650 will put 30 amps into a battery bank for around 5 hours - or all day long if you add another 0.6 gallons of fuel and if the batteries will take that current that long.
The EX650 will do it quieter, too. Remember that the EX650's noise level is 54 dB at full power output and the newer Honda's are 53 dB only when idling. So ... the new Honda's will be running a ways above their 53dB idling noise level while they're powering a 30 amp charger, but the EX650 will be no higher than 54dB while it's running the same charger.