I have almost 7k on my truck since I got it (10/21/2020) and with the radio on you don't hear the engine unless it is reving into the 3k+ RPM. I keep the volume fairly low because I like to hear if something changes in the trucks normal sounds. This isn't my first diesel so I'm used to kind of blanking out the noise. The 3.0 is no where near as noisy as the 6.6. I've had several people ask why I have a Duramax emblem on my hood of a 1500. When I pop the hood and they see the Duramax on the engine and hear the slight rattle from it they are shocked they couldn't tell it was a diesel with the hood closed.
Plenty of power at low RPM (460 ft/lb at 1,500 RPM) and excellent fuel mileage. No, it will not out run a 6.2, but it will get 550-600 miles on a tank of fuel that is cheaper than 91 octane (at least in my area). I don't see a 6.2 going that range between fuel stops.
You will not be disappointed with the 3.0. In my 7k miles, I've averaged just shy of 28 MPG. That is a 4wd crew cab truck. My wife's 2020 Equinox (2.0T AWD) only averages 22 MPG and she drives like a grandma on a Sunday drive.
I will get the 3.0 again if it is still available in 4 years when I get another truck. The only difference in another truck is I will get either the LTZ or High Country next time. It is nothing on the RST (I love the truck), but there are a couple features that I'd like to have that are not available on the RST (cooled seats, surround view camera).