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Just a thought... Apple should consider developing Quicktime and iTunes to accept mod files... Would this development be impossible or just a waste of time?
That being said, don't assume that Renoise is "better" than OpenMPT - they are both just different responses to the same thing. If they're used professionally, you won't be able to tell them apart, or tell OpenMPT frame FLStudio, or Renoise from Cubase. It's all in getting to know your tracker, its limitations, features, and quirks.
I'd recommend OpenMPT. I've been using it for many years now, and I've found it really fast and intuitive. If you're completely new to tracking, it's a good start, because of it's traditional Windows interface. Check out the Modplug Forums for more info, and to ask specific questions about it. There are a couple of people from here who are also over there. In fact, once you start to know people, you'll run into them all over the "scene" websites. 