Zuki remember I also had a pa3x and two pa4x units....besides almost every other KORG arranger since the First one they released in 1980 the SAS 20 personal keyboard lol......ok back to the pa3x vs pa4x in short compared to the Pa4x all the 3x quirkiness is gone on the 4x and it just out of the box sounds better, new styles and fills and sounds are all reworked to a point where you can really hear the difference when playing it hard to explain, tilt display is so nice, clear, bright, to be able to audition styles off the usb is a BIG plus too, songbook is amazing for live playig.....the workflow is improved when editing too. keybed is just right,...sound samples are just better to my ears which in turn equals better styles & sounds all around compared to the 3x. of course there is sooo much more that can be told just go for it, dont double guess yourself, and dont look back, just do your homework when you get it start new you will be surprised at how your music will improve and and all the new stuff you will find inside styles & sounds.. too much to discuss all here..
hope Don M chimes in with more...