I am on the fence on whether to purchase the P10 or OB-X8. I just wondered what it was that got you to settle on the P10?
I got the P10 first because it was released first.. I think the release was really kind of a monumental moment in the second coming of the golden analog age... especially considering Dave Smith's passing not too long after, I just feel lucky to have it and glad Dave did the reissue.
Then the Oberheim merger and the OB-X8 announcement. Another dream come true... the keyboard version was too large for my needs and I'm thrilled they released the desktop version. Also being more of a wheel guy than a lever guy I like being able to use whatever MIDI controller I want with it.
So I didn't choose one or the other, I needed both. But I also bought them some distance in time apart, as owning both is not a small expenditure! I'm also never giving either up. They are different instruments that can sound similar when demanded to, but don't by default.
I've heard some describe the Prophet sound as more "natural" and the OB sound as more "synthy". I could somewhat agree with that, I think the Rev4 is better at producing tones that sound like acoustic instruments, but also sound synthetic. The OB-X8 seems more geared toward lush sounding synthetic sounding tones -- the oscillators have this relationship to each other that just sounds beautiful. As others said, the Prophet is more immediate, the OB-X8 more fiddly while also having so many sweet spots you feel like you can't go wrong. I often run the Prophet through outboard FX, such as the Strymon Mobius to chorus/stereoize the sound. Right now I have the OB-X8 optionally running through a Boss DC-2W, but honestly the OB-X8 can easily sound naturally chorused (widened and modulated) without any FX so sometimes I leave that off. The Prophet's mono sound comes in strong and hot and thus benefits a bit more from chorus? At the same time I've heard Rev4 owners say that it was the first synth that did mono bass and lead better than their Model D, so sometimes that sound up the middle is what you want. I also think that's one factor that makes both synths sound good together -- get them both if you can, even if it takes some time.