The difference is simply the fact that you can still shake a dropshotted worm in place even if the leader is shorter. You can't do this with a splitshot because it moves the weight and pulls the bait away from the spot. A subtle difference but it will make a difference especially if your dragging over deep bedded fish. Instead of moving the bait out of the bed, you are able to shake it right in it.

Does this help?

Rob and Says,
  There is a huge difference in the way a plastic reacts split shotting vs drop shotting.  And trust me, leader length on both rigs can make a BIG difference.  Twice last year, I had the humbling experience of being out fished by guys who's drop shot leader length was different than mine.  Same bait, same water, same technique, vastly different results....
  The biggest difference for me in drop shotting vs split shotting is how I want to move the bait.  I split shot / carolina rig when I want to cover more water and not certain where exactly the fish are holding.  The bait swims more with split shot / carolina rig.  Looks more like a small bait fish swimming along the bottom.  Drop shotting for me is more of a target bait.  I know where the fish are holding and I want my bait to go right there.  Also the bait looks more like a dying bait fish.  It will jump up off the bottom and slow sink straight back down.  It will jump up off the bottom much more vertically than split shotting.  Each has it's place and can be deadly.  Most of the time switching back and forth will produce an extra fish or two from a given area.  Not all fish will react to a single presentation.  Changing the presentation or bait / color can get that extra fish or two from the area.

My .04 cents worth

Mark

I do have my own show.  It's called how to finish in the top 20 at your local bass club tourney.  It's then followed by a weekly special, how to let those around you out fish you while working the same area's.  A new one is in the works though.  Called "How to get two really small bags" for serious tournement fishermen.

Mark

AAHHHHH!!!!!! That was funny MarK I am cracking up!!

There are a few I have made, one is "How to lose #5 at the boat and lose a tournament" or "The art of losing your boat down the interstate at 60 mph" Thats a crowd favorite. Or the one "How to kick several rods over your boat at Once"

I like the last one Glenn.

T-Dot,

You can drop shot any size bait. Heck I have caught fish drop shotting 6" worms. Its the action that you impart in your bait that matters to the fish.
Russ