I've tried some of the J&D basses, and I'm pretty impressed! For the price, they actually produce reasonably tight and usable sounds. The model I tried had a Stingray style bridge pickup and a J-style neck pickup.
With the bridge soloed, you can get a pretty decent funk sound for both slapping and sixteenth note funk. The neck pickup produces a nice, wide tone that is pretty versatile. With both pickups blended, slapping on the relatively new strings was pretty wicked sounding. Had enough high end zing to take heads off. Oh yes, the electronics were active, and offered some flexibility. Overall a good bass for the price, thought I would have preferred them to sound a little warmer.
As for the OLPs from Davis, I've also had the opportunity to try one or two. Passive electronics, two volume knobs (one for each coil), one tone. Good for tech morons like me. The sound is more like a Fender Jazz Bass with both pickups backed up against the bridge. Pretty warm, while maintaining good focus throughout all registers. They don't sound anything like the real thing, but are pretty musical sounding.
I would vote for the OLPs, as I'm a fan passive basses.