the batting dictates the density of the required quilting- so decide how you want to quilt it then choose a batting that meets your requirements.
some batts have to be quilted every 2" (very dense quilting) some you have up to 10" available between stitching lines
and i would take into consideration if it should be a really warm quilt or a more light-weight, cooler quilt.
poly batts are very warm (because they do not breath)
wool batts are wonderful to work with, fluffy, soft, lightweight...warm in winter=cool in summer
batts come in many loft's also= from very thin/flat to very fluffy-lofty.