Interesting. I grew up in the heat of the Coal Region and "hoagie" was definitely the default term used throughout my city. I suspect the linguistic split in that region is probably dictated by the historical percentage of Italian-Americans in the particular city/town, with the more densely populated cities falling on the hoagie side, and the more rural areas splintering off toward the "sub" side. That said, I wouldn't be surprised if the usage of "hoagie" has declined in recent years given the large number of New York City-area and Hispanic transplants that have arrived in the area in the past 20 years.