It's interesting to see different perceptions...where I grew up, I don't think it was a geographical thing, but my mother called it supper. I felt like it was a "poor" family's way of saying dinner (my mom grew up in the depression). My childhood was like a 'riches to rags' kind of story after my dad passed away when I was very young. All my 'rich' friends' families called it dinner, so I vowed when I had a family, the evening meal would be called dinner.
As soon as I was married, I started calling the meal dinner. We moved to Nebraska for my DH's job and LUNCH was called dinner and I confused quite a few people! Today, it is dinner and I rarely hear supper.
It's funny though, because I JUST had this conversation 2 days ago with my DS!