Tailpipes Vs. Dumps: What's the sound difference

[TIMSPEED]

Currently I've got NO tailpipes. (Just have the piece of pipe on the mufflers that the factory puts on; about 4" long)
My question is, what kinda sound different am I gonna get, if I put on a pair of dumps (or turndowns, whichever you call em), OR if I get a set of tailpipes that exit before the rear tires (like Cochino12 has)
Right now, you really can't hear the exhaust, other than a big vibration. (More of a FEEL than a sound)

In case anyone wants to see what I mean...