Go for the 10-spd. I have a 2024 3/4 ton and 1 ton dually. We are now at over 100k miles between the two. The 3/4 ton doesn't tow as much and I have had zero issues. The 1 ton tows a couple times a week, 10-16k depending on the machine I am moving. Both trucks are used for construction and also spend time at the farm, have been great. Had an issue with the 1 ton and GM replaced the valve body in the transmission, it was down for 3 weeks which sucked, but it was all covered. It tows great and I really like the 6.6 L8T. Maintenance has been easy, I do all oil and fluid changes myself. The front end is greasible, so make sure you keep everything lubed up.
On our 2018 3/4 ton with the 6.0 I just had to use our unlimited powertrain warranty. I thought the warranty would never actually pay, but once they saw the engine was spotless inside at 180k and the only issue was a failed camshaft bearing, they paid 12k for a new engine. Always thought those warranties were a scam, but if you are diligent about maintenance and keep track of your records, they are great. Many of the oil changes were self performed, but I had all the receipts from buying the oil and filters, and had a log with the mileage I changed it at.