Thinking about the 20 or newer if I can afford it. Anybody with knowledge comparing the two?
As mentioned above, I have a 2015 and 2020. I love both trucks and have no plans to get rid of either one. The 2020+ trucks are still fairly new, so we haven't seen many high mileage 3rd gen EcoDiesels. Longterm durability and reliability are unknown at this time, but the platform appears to be reliable. The forum is very familiar with the issues surrounding the 2014 - 2019 2nd gen EcoDiesels. It really boils down to your budget.
The 2020 is the better tow rig (no cooling issues, more power, and higher towing capacity). If you decide to get a 2014 - 2019 EcoDiesel, I would encourage you to put away $100 - $200 per month for future repairs.
In stock form, your intake will gunk up eventually and will need to be replaced. Depending on how you drive the truck, your stock intake might last 300,000 miles or it might last 150,000 miles. The 5 year/100,000 mile powertrain warranty is very nice, but that warranty is nearly gone on the 4th gen trucks. It's hard to believe that my 2020 is already two years old (only three years left of powertrain warranty).