I had an awful experience with my previous vehicle. 2018 GMC SLT 5.3 6 Speed.
I purchased it CPO and had all of the transmission issues which everyone here experienced. Many times having to pull over on the side of the Interstate and restart the truck so it would go past 2nd gear. After all most being rear ended by another vehicle with my wife in the car I traded it in for a loss of 4k. 2020 RST 3.0, so far this truck has a superior transmission (10 speed) and engine combination. I love GM so I hope to avoid further issues and went new so if it does happen I can file lemon law. Due to buying the GMC CPO I could not file for lemon law. BE WARNED.
I purchased a 2020 RST 3.0 about a month ago. So far I love the truck, as my 2018 GMC SLT transmission went out. The 10 speed has been more enjoyable than the six speed. 1,300mi on the truck.
NOTE: Truck did leave my wife and I stranded on I-75 due to turbo. Apparently a clamp was never " Installed " from the factory. That was at 400 miles on the clock.
* No issues sense then.