Having been born in PA and living in the country, I always thought it was supper.  Then, once I became an adult I started hearing people say dinner.  I've lived in a few different states and started to observe the difference.

When it comes to NY, there really isn't a specific area that says dinner or supper but more of an age range. However, not really.

The average age group that I've found that says supper is over 60. When breaking down areas in the Hudson Valley, it's a pretty even amount except in Poughkeepsie.  There seems to be more people that say supper than dinner of all ages.

They mean the same thing, they are universally known but not much in different areas.  I did notice that it depended on areas of Poughkeepsie that used them more than others and when talking to people. some, like myself and my wife seem to use supper when in the company of family and older people but dinner when talking to friends or making plans.

I talked to one gentleman in New Palz that said 'you have supper at home and dinner in a restaurant on a date"  He brings up a good point.

What do you call it?

Whatever the case, there are plenty of places in the Hudson Valley that you can meet up with some friends for a nice dinner.  Also, my wife is an AMAZING cook so anytime, you are welcome to come for supper.