Bertram,
I don't think anyone here is trying to convince you are anyone else that the Honda is "The Only Way To Go". But it may, just may be the best way to go.
You are correct the Yamaha 2800 will run your AC, that is will run it some of the time. If you ever travel in any altitude it may not be enough. It is also louder and quite a bit louder too. With two of the Honda 2000 you have the option of using one if that is all you need, but the second one is there if more power is required and that will "Probably" be the case some of the time.
The Honda is also in my opinion a better unit. While i do not and never have owned a Yamaha 2800, I have had three Yamaha 1000 watt units. All three of these lasted almost exactly the same amount of time, and that was right around 600 hours of run time. After that the motors where shot and I change oil every 15 hours. One of the two Honda 2000 I have now has 1285 hours on it and is still going strong, I had this Honda in for service last week. they decorbanized the head and found very little wear.
I personally don't have a dog in this fight, don't own stock or get money from either Company. But in my humble opinion there is no comparision between the two. None!!
Gunny