Yes the guitar sounds on the PA500 are very good and realistic and indeed very deep. The only thing you miss are the DNC sounds. If you can live without that the PA500 is a very good choice and you can fully edit the voices as a real synthesizer. Check out http://www.korgpa.com/pa_root/en/products/pa500.html?en for more demos.

Would you please say more about DNC sounds? Is it something that S910 has?
Also do you mean that PA500 has the ability to modify sounds, like a synthetizer, but S910 does not?

Yes Kami DNC is what Yamaha called SA. The sounds on the PA500 are fully editable and on the S910 not. Not much to change on a Yamaha arranger. That is one of the many reasons I choose a Korg

So may be with editing some sounds on PA500, we can reach something close to SA sounds and use it live. Correct?

No not exactly. If SA or DNC is important to you you better buy a PSR S910 or Korg PA800. I have already seen the PA800 for a very low price because of the arriving of the new PA3X.

Since I can not try these keyboards in person, it is difficult for me to say if I need SA/DNC sounds or not. But when I see youtube videos, guitar sound on PA500 does not sound much different from S910. I am totally confused.

I think because you also like synthesizers the best option for you is the PA500. The sounds are very good and deep on it. Also it save you a lot of money. I own my PA500 for more then a year now and still very happy with it and the edit possibilities are endless.

I agree, this editing ability looks interesting to me, so it is like I also have a synthetizer, which gives more understanding of the keyboards.

I contacted two persons who have guitar sound videos on Youtube and have used both keyboards. First one said Korg sounds are more like listening to live music in front of the band, while Yamaha sounds are like listening to concert or CD music. I think he is right, since it describes my feeling about guitar sound on S910. Beautiful, but not live and deep.

Unfortunately, the second person said he has broken two keys in a year, mostly because of playing guitar pieces. May be an extended warranty solves this problem.

BTW, both said, both PA500 and S910 are amazing.

Broken keys? Is the first time I hear about this. Only problem I know is the joystick of the PA500. Mine got broken after 9 months. Many people have had problems with the joystick.

I searched the web and it looks joystick is really a big problem in PA500. Many have broken it.

If PA500 works as a synthetizer too, then what are advantages of M50 over PA500? They are at the same price, M50 without speaker. So there should be some advantages for M50.