I've had both (Tribute).
The SB-2 is very high output (been mistaken for an active by sound engineer), and it's really its own tone. Body is smaller than a regular P (cinched waist). Neck is Jazz width, but reasonably deep front to back. No tone control, as already pointed out.
The LB-100 is G&L's P bass - "regular" Alnico split P - very nice sounding P pickup. Body still a bit streamlined vs. a regular P but not to the same degree as the SB-2. Neck is P width. Regular controls (vol/tone).
IMO If you want a P bass, get the LB-100. If you want a quintessentially G&L product that kinda looks like a P, get the SB-2.