I prefer 100% cotton quilt batting for lap quilts because it drapes well and becomes softer with every washing. It requires close quilting, however (max 2" apart). The one I use is Mountain Mist Blue Ribbon.
The problem I have with Warm and Natural is that the drape is somewhat stiff. This is actually a bigger problem with smaller quilts; it's not as noticeable in larger quilts, although then the weight becomes a problem for me.
There are other batts that are soft, but I haven't tried most of them. Hobbs 80/20 is nice if you want more "puff" than MMBR.