Here are a few more generalizations (tongue also in cheek) from my own experience in both worlds:

Folkies tend to be:
-better educated
-higher socio-economic class
-more rule-bound at festivals (low chairs in front, full-height in back, no high-back chairs in the audience pulleeeeeezzz! enter by this gate, camp in neat little squares of this many square feet, etc.)
-better singers and likely to sing along in the audience
-more diversified (race, sexual preference, ethnicity, religion)
-more likely urban
-more interested in the lyrics, message

Bluegrassers tend to be:
-better instrumentalists
-more interested in tradition
-more formally dressed on stage (my husband insists on wearing a tie when he performs to show his respect for the music and to counteract the hayseed image)
-rural or small-town
-interested in lyrics that continue the "tradition" and "values" embraced by the bluegrass "culture"
-more fun

One should never generalize. (I've got dozens more...)