I am a life-long New York State native, and I actually did a study on this in college! (seriously!)
I have lived in Waverly, New Paltz, Corning, Albany, Rochester, and NYC.
and my fiance is from Buffalo..I have the state covered!
I grew up in Waverly, NY, which is on the NY/PA border between Binghamton & Elmira..we were firmly in "pop" territory, and I never heard it referred to as "soda" until college..
I went to SUNY New Paltz, in the Hudson Valley, (across the river from Poughkeepsie) and many of my college friends were from Long Island..they all grew up with "soda" and had never heard of "pop"!
So, by doing some research and asking many New York natives (college friends) from all over the state, I found out where the line is..
Buffalo, Rochester, Corning, Elmira, Waverly..all firmly "pop"..
Long Island, NYC, Hudson Valley, Albany..all firmly "soda"..
Syracuse, Ithaca, a mix! probably because of the large college popluations..
and also they are in the middle of the state.
So! there is a distinct pop/soda line that can be drawn through the middle of New York state..it runs from Oswego, through Syracuse & Ithaca, and down to Binghamton..west of the line is Pop, east of the line is Soda..
the further west away from the line you go the more "all pop" you are..to the point that Buffalo is ALL pop and no soda..
the further east from the line you get more and more soda you become..Long Island is all soda and no pop at all..
(the only area im not sure about is the Adirondacks..seems like they should more popish, but I havent surveyed there yet, so they could either)
near the line is a mix..thats where the blending of the two cultures occurs..
Scot