Honda or Yamaha inverter generator?

You haven't indicated just which size of genset you're considering but having previously owned 2 Honda EU2000i gensets I'd give the nod to the new Honda EU2200i which is priced the same as it's predecessor but weighs much less than a Yamaha EF2400isHC. Equip your trailer A/C with a MicroAir Easy Start Soft Starter Kit and your chances of successfully starting that A/C even at 90F and higher elevation are pretty good according to those who have done this mod, obviating the need for a larger, heavier genset.