My biggest experience with SB comes at the U21 level so I'll use that for my example. I find that SB being within a couple(say 14 ID 12 SB) make the defense better. SB has also been talked about in other forum posts(I don't have them handy so my apologies) on being necessary to run zones.
Totally concur. ID I feel is about positioning SB the ability to disrupt the shooter. Being someone who has pretty much played only zone for many seasons i notice a big is there to disrupt guards who venture down the lane. But you better have some rebounding as well, especially in a 3-2 or you'll get pounded on the offensive glass