When you enter a quilt in a "quilt show", it will be judged and seen almost exclusively by other quilters so their standards will be more to do with the technical aspects.
At a "fair" your quilts will be seen by a larger variety of people may be more about first impressions, pretty colors and visual interest and don't care a hooey about how perfect the stitches are.
Like someone else said already, I enter contests to push myself. I put an art quilt in a recent fair and the judge's comment was that it wasn't evenly quilted over every area. True, it was not. True also, it wasn't a bed quilt and not very large and didn't need to be evenly quilted, but that was the judge's standard. Ok by me, it's a fun quilt to look at and I got lots of nice comments from people viewing it.