I've played both over the last 26 years. As someone already said, the Signatures are more refined and "pretty" sounding. The 2002's are the quintessential classic rock cymbals, can't go wrong with them.
I wholeheartedly disagree with Signatures being any louder than other cymbals. Brighter? Absolutely! But it's physically impossible for an 18" Signature full crash to be louder than an 18" 2002 crash, there's no way that either could move more air than the other. It's a trick of the ear: we perceive higher frequencies to be louder than lower frequencies. Since the Signatures are brighter & clearer on the top end, that must be what everyone is perceiving as "louder".