i use to try to comparison shop but i always found that for the stuff we buy, nothing could beat walmart for general grocery trips.... food lion (a southern grocery chain) was the best for chicken and meat on sale...and aldies was the best for bread and dry milk. so i basically stick to that schedule and it avoides lots of headache.
oh..and we dont have a warehouse near enough to make it worthwhile - no costcos around here and sam's club is about 15 miles away on the interstate...so i rarely to never bulk shop. when i do, i've found that snack cracker packs (which my husband eats alllll the time) are cheapest there as well as swanson broth (which i use a lot). so i get those when i happen to be in that area and with someone who has a membership!