There couldn't be an argument that IGRT isn't as good as IMRT just based on the fact that IGRT is "enhanced" IMRT. It might not be any better if the doctors and technicians doing the treatment plan were just really perfect and got it all right all the time, but it can't be any worse.
I saw the "IG" part, my Calypso markers, as a control point - a constant recheck that I was lined up right. If something moved internally, it stopped the process. Because the markers emit a unique id, it also identified me to the machine and the Techs. In my case that wasn't an issue - it was a small clinic, and we all knew each other by first names about day three, but I can see that flashing up a picture of the patient and verifying the plan in use each day would be very important for a large volume hospital. We have had some members post their "journeys" in which they rarely saw the Techs even a second time.
From what I understand Tomo therapy is IMRT with the daily mini-CT scan, so just a variation of IGRT.
Yes, you might be offered only IMRT if they don't have the extra imaging equipment. Take away the Calypso scanner, and mine would have been IMRT.