It depends on how you plan to quilt them. If I am FMQ ( free motion quilting) them I use Hobbs 80/20 batt since it is more stable with cotton fabric. Polyester batts from Walmart have a nice loft but the fabric tends to slip around on it and I get wrinkles in my backing fabric. There are a number of 80/20 batts on the market and I recommend them for your first effort since stuffing a quilt with polyester batt through your machine can be difficult also.
If you are hand quilting, use the batt you like best for the loft you want.