You can make an SB-1 or SB-2 sound just like an LB-100, but you can't make an LB-100 sound like an SB. On the SB, if you just roll the P pickup back to somewhere between 80 and 50%, it sounds just like a regular, old school P bass. With the SB-2, you need to add a Tone control to cover all the P/LB-100 bases.
If I were looking at a choice of a Fender P, or a G&L LB-100, SB-1, or SB-2, I would absolutely go SB-2 every time. It can give you anything any of those others can, plus more, that the others can't. As I said, that's if you add a Tone control.
You can add a Tone control for about $10 - 15 worth of parts and roughly 30 minutes of labor. And the modification is fully reversible.
I did this to my SB-2. Actually, I spent an extra $5 or 10. I preserved the individual volume controls for the 2 pickups and added a Master Volume and a Tone to mine. Now, it can still produce all the same sounds it could when it was stock. But, the Tone lets me do the serious P Thump thing, too.
And, like I said, it's still totally reversible to put it back to bone stock with no sign it was ever modified - because I used 2 stacked pots. Not that I would ever put it back to stock. My SB-2 is the last 4-stringer I will ever let go. It's only second in my herd to my EBMM Sterling 5 H.
You can check out this thread if you want to see for yourself that an SB-2 can do EXACTLY a traditional P sound.
http://www.talkbass.com/forum/f8/p-vs-p-like-can-you-tell-difference-838140/