read the packages and choose batting that allows you to quilt your quilt the way you want to- i seldom purchase my batting ahead of time- when i do i usually wind up having to switch it because i choose a different way to quilt it-
some batts are good for hand quilting-some not so much
some batts allow you to quilt up to 10" apart
some batts need to be quilted every 2"
some batts shrink more than others- some batts hold up to lots of washing/drying-dragging around-
some batts are more fragile and are more for the quilts that get put away.
the package holds a wealth of information
i keep a (batting journal) i try every new batt i come across-
i cut a 6" square from it- to add to my journal- i include where it came from, how much it cost- it's fiber content- the loft, the quilting recommendations- the care instructions---then after i use it i add notes on my feelings about it- did i love using it? did i hate it? did it cause alot of lint? and how did it wash up after the quilt was finished-
that way if something goes on sale i can check to see how i feel about it --- it might not be such a good deal if i hate the batt.
i love wool batting but it tends to be a bit expensive-
i love dream poly for kids quilts- it takes a beating and washes up beautifully
i love warm & natural for many long-armed quilts
i love hobbs heirloom batting for hand quilting
there are so many wonderful batts to choose from!