I checked out the link that rebeljane provided. 1/4" is pretty thin for many quilters. I personally like that loft, but it is definitely on the thin side for polyester batts.
It's hard to find loft measurements for other polyester battings to make comparisons. I noticed last time I was at JoAnn's (several months ago) their bins had loft measurements. My memory isn't the best, but I think Hobbs Thermore -- which is considered a very low loft batting -- was around 1/4". Hobbs Cloud Lite, which is considered a low loft batting, is 3/8" thick (
http://www.hobbsbondedfibers.com/products-retail.html ). Hobbs Cloud Loft is their highest loft battint at 5/8" thick, so I'm thinking Hobbs PolyDown is probably 1/2" thick.
I like Hobbs PolyDown for soft quilts that will dry quickly, but it is a little more difficult for me to machine quilt on my midarm frame setup than Mountain Mist Quilt Lite (
http://www.mountainmistlp.com/products.htm ) which has a stated loft of 1/8"-1/4". The look of the Quilt Lite was definitely flatter than the PolyDown but, as I said, I like the flatter vintage look a lot.
A quilt made with any of the above polyester battings will be a lot lighter in weight than one made with Warm and Natural, and will also dry much faster. Someone who is used to Warm and Natural may think the lower loft polyester battings are too thin; however, the flat look of the quilting will be very similar. It's just that the WnN will be a thicker and heavier flat look.
Edit: In terms of wear, I think the polyester is similar to cotton as long as the quilting is moderate or close. If quilting lines are 12" apart or the quilt is tied, there will be no comparison -- WnN will wear much better.