Both generators will be fine with running a air conditioner and also run the microwave. Neither is able to run two A/C's at the same time, and you would need to shut off the A/C if you where running the microwave and toaster or other large load such as a 1,100 watt coffee maker or such loads.
The bigger question is how many miles a year you plan on putting on the RV and if the more expensive diesel engine is worth it or not. It has more expensive fuel filters that need to be changed more frequently, and typically has a $150 oil change, not the $35 oil change that a van or pickup with the familiar V10 would have.
Fred.