You have just demonstrated why it is of vital importance to try before you buy.
Regarding the PA900 then like Yamaha these were aimed at the more mature home hobby player/OMB who play older more traditional music, unfortunately this market is in serious decline as users in this category are quite simply dying off, most of the younger generation do not want traditional styles and sounds as they don’t meet with the type of music they enjoy and play, thus if Korg want the arranger line to continue they have to adapt them to a younger audience. (Give it another 5 years or so and the arrangers we know today wont exist as there will be very little market for them (Manufactures moved their workstations/synths over to a younger generation donkeys years ago, as they knew the traditional users were dying off (They also made much cheaper models as the wealth of the young has declined compared to the previous generation)
Another thing to remember is that Yamaha Arrangers came from their home organs, (So where more friendly and traditional) whereas when Korg started producing arrangers they were simplified versions of their pro keyboards (Hence they had a reputation of having a difficult OS as the terms they used came from their pro line of boards, and were completely alien to the home player)
If you are going to have two boards, then try and exchange the PA1000 to the Yamaha PSR975 and use both together via Midi on a 2 tier stand and you will have a combination that no single arranger will be able to get close to. (If you have the room and time to add and learn bass pedals do so, as the arranger doesn’t know what chord you are going to play next (Unless you modify your playing style, but why should you need to) thus the bass lines are not a good as they could be)

Bill