Working in a hospital for over 20 years, I have seen my share of spider bites and their effects (I worked in Pathology) where we would get the "remnants" of the infected wound. If given the choice between being bitten by a Black Widow and a Brown Recluse, i would choose the black widow every time. Brown recluse bites will just deteriote the skin and have it fluff off leaving a gaping whole, while a black widow will just leave a painful bump and a quarter size redness around the bite that itches like crazy (don't scratch it ever).
Actually one of the most poisonous spiders known to man is the "Daddy Long Legs" but it's pinchers aren't strong enough to penetrate skin, so we don't worry about it. If you do a search on the net asking for infected wounds of brown recluse spiders, you will see some of the nastiest pictures you can imagine.