I'd be surprised if SP5 is somehow better in any meaningful way compared to SP4.
For previous iterations there was always something "wrong" with the old so there was always something to improve, but current versions are pretty good as they are. It is difficult to find much to complain about them, other than maybe the prices.
Things that I'd want: 10bit colour display with DCI-P3 / AdobeRGB colorspace + HDR support and properly working colour management in Windows. Other than that better specced fanless models for cheaper, but I wouldn't hold my breath on either of these.