I have been quilting since 1988 and used poly in a couple of my quilts and didn't like the bearding at all. Once I started machine quilting, I found that I liked cotton batting or hobbs Heirloom 80/20 batting; poly batting slips. when you're machine quilting, cotton sticks to your fabrics.
My hubby sweats far too much under a quilt with poly
batting in it.
Sharon W.

I only use polyester batting, it doesn't shrink like cotton will and warm and natural shrinks also. All 92 Quilts and comforters I have made in the last 45 years has polyester batting inside them.
It is very nice to work with. I used warm and natural in a bird cage cover and it shrank when I washed it and dried it, polyester has never done that. We sleep under a quilt all year round and have no problems, heat in winter and A/C and ceiling fan in summer.

Depends on what I want the quilt to do.

If I want it real traditional, or if I want it to be a true, warm bed quilt, I use cotton.

If I want it lightweight and "breathe-y," that is to say not hot, then I use polyester.

If I want it thin and drapable, such as in a mini, then I use a very thin polyester.

If I want it durable such as a tabletopper then I use cotton - which also accommodates possible hot dishes.
.

I usually always use warm & natural.

If you want to try it, go for Hobbs Tuscany Washable Wool. I didn't feel that it was all that much more in cost but Oh what a difference in a quilt. It quilts beautifully and feels wonderful, drapes beautifully. Can you tell I really like it.

New quilter here, and I'm confused. (Not that I'm new to being confused or anything. lol)

Anyway, I'm taking a beginning quilt class at my LQS and our teacher told us that cotton was for machine quilting and poly for hand quilting. What's the reasoning there? I think she said it had to do with how the batting binds to the fabric of the quilt top??

I use both the Poly - I buy the thin type I get from Hancock of paduca and it is soft and drapes beautiful and get my 20/80 warm and natural from joannes - I enjoy them both - the difference is that cotton breathes and poly keeps body heat in ... I use poly for quilts that I use in the winter when guest come and we turn down the heat in the house (at night) so they won't get cold. I have a scappy quilt on my bed with poly and it is the only blanket I use because I get too warm with more than one blanket on me at night. But I think every one should use what they like.

Judy, I second that confusion statement.

There are no steadfast rules when it comes to batting, it's more a preference thing. That was the teachers opinion.

I think warm & natural is better for me to machine quilt.

I agree Kate, it seems more stable. I seem to get more puckers when I have used the poly batting.