Actually it's 87%....But they are worthy of discussion. The rest si an upgrade that could not have been done via software. Some of which brings it to the Korg Standards as in the Controllers. Others the new Rolands with the TFT screens. The additional voices and the new RFX engine allowing 5 EFX per style required more than a firmware upgrade.
The additional voice paks mean more to me than anything else as I don't mind paying for styles,voices and of files that I need. My time is worth more than the miniscule $3-$7 cost of styles and or MIDI files. That's one of the reasons I prefer Yamaha. I can buy anything I need without leaving the keyboard!!
Everyone has their favorites. I at least HAD a PA2X for 16 weeks, I don't see anything in the upgrade that's making me go.."oh Shyte shoulda kept the PA2x". If I really wanted the Korg Id buy a PA800 tomorrow. Everyone hears things differently no one is right.
BTW All the lower end Yamahas have score and Lyric readers....I don;t see that as an upgrade Yamaha has been doing that for years.