As a consumer, how should I determine whether to get a 4.7 iPhone 6 or 5.5 iPhone 6 Plus?

Answer please.

You need to ask yourself just one question:

Does size matters?

Depends on who you are.
I already know I will not be getting a 5.5 inch model. I don't want a phone that big, and I will avoid getting one for as long as I possibly can.
On the other hand, I know people who would never consider the 4.7 inch model - which is why Apple is introducing the 5.5 inch in the first place.
And then there are people who don't know yet. They love their iPhone, would never get an Android or Windows phone, so they never seriously considered anything larger. Those folks need to go to the store and see for themselves. Put it wherever they like to carry their phone, hold it the way they normally hold a phone, see how it compares in terms of comfort with the 4.7 inch and also their current phone. I doubt anyone would actually prefer less screen real estate, so it's all going to be about how the phone fits them, physically.

Try winning one!