For the iPhone 4 and iPhone 5, I was one of those people who preordered and had it delivered on release day.
For the first time I'm not going to preorder, I'm going to wait a few weeks after release, let the dust settle, and physically hold the phones in my hand at the apple store then choose. I have no clue which would be better / more comfortable in my hands. Who knows...
There should be an option for "undecided"
4.7, that is assuming the specs are the same else wise.
I'd only consider the 5.5" if its significantly upgraded over the 4.7" model. When I say that my example would be if the 4.7 used the current A7 processor while the 5.5" uses a new A8 or something to that effect.
Even then I'd have to handle the 5.5" but I feel that would be too big for me to use daily.