Hi,
Like many others I now usually use only cotton fabrics for quilting. The first 20 years I used anything that struck my fancy. I will say that cotton has improved over the years or else it is just the cotton sold by Quilt stores. One advantage of blends is that they don't require as much ironing and do hold their color better.
If I am making a quilt for a child or a person I know will not care one way or the other I can use a blend.
If you were going to enter your quilt in a juried show for "traditional" quilted items it would have to be cotton. In my experience about half of the work at today's big quilt shows is anything goes. Art quilts in particular can be made of anything even none fabric items.
I am going to the show in Lancaster PA tomorrow I will report back next week.