Question for those far more knowledgable than I on things FN. Is there a functional and/or features advantage in owning a USG model instead of the "standard" black FNP .45? I ordered the USG but the distributor sent the FNP 45 instead. If there is no real difference I'd be just as happy with "basic black". What do you think? BTW, I'm new to FN products and this forum, so hello to all.