Howdy Mac,
The principal difference b/t Lancaster and Grove City is that GC is indisputably a
suburb of Columbus. It sits in Franklin Co. and is directly adjacent to the capital city.
Lancaster is very much a separate community in its own right, with a distinct culture and atmosphere apart from Columbus. It's the seat of Fairfield Co. and in fact, although many Lancaster folks
do commute to the City for work, Lancaster residents in general pride themselves on
not being part of Columbus. (That's one of the things I miss about home, frankly!)
Some commonalities b/t the two: Grove City and Lancaster are both semi-rural, offering easy access from the surrounding countryside. They're both a little slower paced and much friendlier than Columbus for the most part, each having a sizable population of Appalachian folk. Both communities tend to relish that "down home" flavor, and people in both places are basically unpretentious, genuine, and courteous. Both places have a wide streak of "heartland America" and wouldn't want it any other way
Not sure about SDA in Grove City, although here's a website for the Lancaster SDA church:
Loving Hope Lancaster OH : About Us -- including Mission Statements and our Ministries
The only other SDA church I'm aware of in the Cols. area is the big, elegant one they recently built in Worthington.
Hope this helps!

Lanc