from what i can tell LI is slightly less effective, but there isn't enough data to suggest that SB does anything more than defend contested shots better. Think of it this way.
First, lets assume a player takes 25 inside shots a game randomly in some crazy LI offense. With his decent shooting ability, you need a decent ID to contest a lot of those shots. If you have a 2 or 3 ID big with 10 SB, then you might get 7 contest shots and 18 open shots, so that 10 SB is still only going to be of any value on less than 40% of the total shots defended. It really only thwarts the percentage of contested shots.
If you can get a guy with 10 ID 10 SB in D.V, or 17/17 in D.II, it might be something of merit (shutting down more than 50% of the open shots, and then blocking a lot of contested lowering the contested make rate from 30% to 10-15%), but right now the cost of each point of SB to a players cap and their salary is far too expensive.
If i went over your head, go watch a replay of a game. when it says guarded closesly or something along those lines, it's a contested shot. Other times a player has plenty of space, resulting in an uncontested shot. on all but 3pt shots, uncontested result in a higher make rate. If that still doesn't make sense, then just know that SB doesn't mean much until you see them reduce the cap hit significantly on SB.