Other differences include a pulse-width modulation of 1020 Hz an even warmer CPU temperature of 85 C on the slower Core i5 IPS configuration. DPC latency issues continue to be present on both the Core i5 and Core i9 SKUs.
https://www.notebookcheck.net/The-Dell-XPS-15-7590-Core-i5-is-quieter-brighter-and-almost-two-times-longer-lasting-than-the-XPS-15-7590-Core-i9.435597.0.html
Thank you for mentioning the poor dpc latency of these. I've been testing laptops for my own professional media uses and dell is by far the worst at tuning their kernel drivers and such, leading to dpc latencies of 2-4ms. Completely useless in live music or video applications