There are, of course, capacitors in the circuit of the L-2500. They can be found on the bass & treble pots as parts of the EQ stack and on the preamp board as support components to the opamp. AFAIK, my new L-2500 has no caps as part of series/parallel switching. I've not looked under the hood of an L-150x, but I believe any differences to be slight (if any).
From a global and aural perspective, the L-2500 on both pickups will be a loud and ballsy bass, particularly in series. I have one of these beasts. On the bridge pickup only, it'll sound, well, like the bridge pickup only. Thin sounding in comparison to both, but with great definition.
The L-1505 has a single L-2500 pickup in the classic "StingRay" location. Being a bit further from the bridge than the the bridge pickup of the L-2500, it's going to see greater string excursion and therefore make a bigger signal. It's also in an oscillation node sweet spot, which also makes for relatively large string excursions, on a harmonic, right over the pickup. The combination is loud, ballsy, and damned aggressive.
I've played an L-1500 as well as its old cousin the Climax. Either of them are more aggressive sounding than my L-2500, SUB5 (poor man's SR5), or Bongo 5HHp. Any of these are basses can rip out the front row. The L-150x throws the front row to the back of the room.
Ken...