Using the Denons as example, the 3600 is one of the better testing units on ASR compared to many others. Are all of those measurements translated into audible differences? Likely not.
With that, I have been looking at the 3600 compared to the 3700 to replace a recently deceased Onkyo AVR. The pricing right now makes me question why I might buy the older model as it is only $100 less than the newer.
For me, I want the value to make sense if I buy that older model. I do not expect any real performance differences.
Moving from there, what are your plans for your system? Speakers you use or might upgrade to in the future? I would consider these items as a requirement for the AVR I buy now. Is that extra 20w of power really making a difference? Whereas the ability to process 6 Atmos speakers might be important to you.
I would only consider the higher tiered model if it worked for my system now and 2-3 years down the line according to my goals.
I use Amps on my main 5 channels and don't need the power from the AVR Amp Stage.
At the same time as the pragmatics, there is also pride of ownership and what makes you feel better about your system.
Only you can decide if stepping up is necessary for you.