I'm leaning toward the 4.7, but it depends on the specs. If the 5.5 has more compelling features, that's what I will get. I also may end up selling my iPad Air if I buy the 5.5. I honestly don't use it enough to justify owning it, but selling a 64GB wifi model would more than likely incur more loss than I am willing to accept.
That's something to think about. I wonder if the 5.5" iPhone will eat into the sales of the iPad at all.
The ONLY reason I even use my iPad is because of the comfortably large screen. I can do EVERYTHING my iPad does on my phone too!