partly depends on what you'll be running with them.
I like the JL amps for their regulated power supplies and regulated output stages, not to mention their rather extensive crossover and filter networks built into the amps, and general build quality. Good amps.
I'm not as fond of PPI now as I was in the old days when they made their Art series amps, but they are still decent products.
i would be using either to drive my 2 w6v2's.. for the pcx, 400w to 2 channels,.. i know the amp is greatly underrated, so the gains would be turned down a bit but still maximize the subs' performance.. the 2400 amp makes 1600+ bridged, which leaves me with future flexibility of upping to RE triple x's, etc..
the JLs are also underrated and i feel i would be content..
just fishing for opinions..
i heard that the same person designed the amps for PPI and JL..
umm, gains have no effect on power output of the amp. the gains are only there to match the line voltage to the input stage of the amp. if you don't want to damage the subs and the amp is rated for too high an output, just don't turn the subs or stereo up all the way.
the 500/1 puts out closer to 650wRMS, and the 1000/1 puts out closer to 1400 wRMS if you want to talk about underrating products but the same person designing two products doesn't always mean both are equal. They were designed under different companies with different ideas.. that'd be almost like assuming the ford escort has to be good because it's a ford, and the Ford GT is a ford.. so both must be equal.. exageration yes, but you get the idea. Anyway one thing to keep in mind is that the JL amps put out the same power regardless of load, so adding a second sub divides the power between them adding a second 4 ohm sub to the PPI amp will double the power by dropping the load, so the PPI may be more suited to your needs. JL's amps match very well to their own subs, but they aren't always the best solution for matching to products from other companies in my experience.