Hmmm. tough decision! Climate wise, I would definately go for Hawaii. However, I looked up the 2, and Hausermann's looks really interesting since they also propagate endangered paph and phrag species as well as other rare species. And it seems to have a very large range of orchids too. I'm guessing that you already read this.
Have you contacted both of them to see if they accept interns? If they do, you could also ask about the activities you would be doing and such, and compare that way. Also, if you've never been to the USA, staying on the mainland would give you more opportunies to visit things.
This is just how I see things, and the final decision is still yours to make!
__________________ Camille
Completely orchid obsessed and loving every minute of it....
I think mine would be Chicago for sure based on balmy weather, easy commutes and plenty of surfing to do on Lake Michigan. Obviuosly, I am kidding. They are correct in telling you that there are many orchid greenhouses in Hawaii. Good luck!