I don't sing so I don't use the vocal harmonizer on my Pa800. However here is what Keyboard Magazine said in their recent review of the Pa800:

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Selecting the “Mic” tab on the Pa800’s touch screen brings up options for types of harmonies, mic EQ and overall effect level, mute icons for your own voice and your three virtual backup singers, plus a talk-over button. The Pa1X Pro Elite adds a fourth harmony voice and pitch-correction. The underlying technology is from TC-Helicon, and since they’re an industry leader in hardware vocal harmony boxes, our expectations were quite high. We weren’t disappointed — the sound quality is a perceptible notch above other arrangers’ best efforts in this area.

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Kind regards,
Tommy

I think that Korg's online Pa800 video tutorial, that RobertG pointed to in another post, covers some aspects of the harmoniser.
http://www.korgpa.com/pa_root/en/support/tutorials.html

your question is way too broad. The Pa800 has features that the PSR3000 does not.

Ask your self the following qurestions

1.Do i experiment with sound creation on the keyboard or assisted by software programmes on computer or rarely if at all ?
2. am i into sampling or would i like the option to do it onboard the instrument
3. Do i write original music and if yes do i want to crfeate detailed songs onboard the instrument or do i use an external sequencer ?
4. Is ease of use really important to me ? Are you familiar with the korg and yamaha operating systems ?

Once you have addressed these questions it wil be easeier to advise you as to which instrument is more suitable for your needs

spalding4. Yes, as you state we all expect and use different facilities from keyboards. Regarding different OS's I'm fortunate possibly in that I don't have a problem learning a new OS, to me it's like driving a new route to get to the same place. The Korg video already mentioned runs for 1hr 15mins and is well done by Korg to eliminate OS learning problems.
Having ordered a Pa800 at the Keyboard Festival Korg gave me a DVD of the Tutorial which obviously contains a better quality bit rate picture.
We spend thousands on all these keyboard and all manufacturers should provide a DVD such as Korg have done FREE.

I agree Graham. I watched that PA800 video on the web, it was great. In fact, it's a great marketing tool for Korg, since it really sparked my interest in the board.

When I first bought a Roland back in 1993ish they produced a video that was very helpful too!

Graham FL