Having a serious obsession with J basses and Rics (I have a 78 4001), they are very different beasts tonally. Rics have a hollowness to the midrange that gives the bass a specific barky honk that is in a different sonic universe to the J Bass. When you drive it through a tube amp you get that Squire/Lee tone, simple as that. I can't imagine getting a tone like this on anything other than a Ric. I use flats at the minute though, so I'm after that McCartney thump which the 78 delivers in spades...
My one also has a great deal of bottom end. I have tried many Rics in the past, however, that had no bottom whatsoever. Try before you buy!