I agree with SIlver- you are just going to have to take a drive and check them out... in my area, JoAnns (a superstore) has more yarn (by far) but equal needles/ notions. The prices are about the same. They both offer coupons.
I personally prefer JoAnns, b/c they have fabric (my Michael's doesn't- just a few fat quarters here and there) and sewing stuff. and actually offer classes. I prefer Michaels for the scrapbooking, kids crafts, house-crafts stuff (wreaths, baskets, cheap frames)
I also like that JoAnns will send you coupons by email. Michaels coupons are only available here in the local sunday paper.
Ummm I'm starting to think I have a crafting problem......