Why would you think the doctors would give it to you if you didn't need it? Why would they order an expensive, difficult treatment if it wouldn't help you?

I think you've asked the wrong question. You don't ask the doctors for chemo, you ask them about chemo. I don't understand why you would be talking to an RO about chemo. You should be discussing that with a a medical oncologist, not a radio oncologist. Now I'm a bit confused about how you are in this situation, maybe I've missed something. I don't know where you are, I presume the US somewhere? In Australia they call it a clinic, I believe in the US you call it a board, where a range of specialists (MOs, ROs, ENTs, dentists, speech pathologists, dietitians) review your case together. They discuss and decide the course of treatment, each specialty discusses the implications of the treatment from their perspective. For example the RO says we're going to do IMRT, the dentist points out that you'll need xyz teeth extracted.

You should not be in a position of having to "choose". Professionals who know a lot more about this than us should be deciding on the best course of treatment and explaining to you how it works. As it was explained to me and as Cheryld just said, it softens up the cancer so the radiation can better kill it.

And if there really was a coin toss either way and they did offer you two choices, I'm with Brian. Nuke it from orbit! I think that is a common feeling, get this out of me and do whatever you need to to prevent it ever coming back.