Unless you have a very specific project you want to work on that they are doing at Arizona and not at Emory then I don't think you'd be able to beat Emory for ID. I know the connection with the CDC is brought up a lot, but it's legitimate and you can't beat it for the broad range of interests it covers for a grad student (so if you go thinking you want to work on HIV and decide later in school you want to work on Malaria, you still have those resources because the CDC has it's hand in everything - where at another school they probably don't have as many top-notch programs in different disease focuses - just a general example). In addition to this we got to meet a lot of the ID professors and talk with them at Visit Emory, most of them are still doing active research within Atlanta and abroad in countries in South America, Africa, the Middle East, Asia, etc. A couple of floors of one of the buildings houses labs for a few of the ID professors where they have student work opportunities. There are also opportunities on the same projects outside the lab in statistics, IT, etc. So there are plenty of ID opportunities domestically in Atlanta and abroad, whichever you want to do. I also think Emory has a reputation for work in ID which would be helpful once you graduate.
I think everyone should choose the school that's best for them and maybe Arizona has something to offer that appeals more to you. But on straight ID, I would say Emory wins hands down.
