I have nearly a dozen Echo devices, ranging from Echo Show 5, Echo Dot gen 2, Echo Dot gen 3, and various others.
In my experience, the Echo Show 5 is the most deaf and the Echo Dot gen 2 has the best hearing. For example, I ask Alexa something while facing the the Echo Show 5 (3 ft in front of me) and the Echo Dot gen 2 (15 ft off to my right) would answer.
I would suggest getting exactly the same model if you are concerned about which device answers because their microphone sensitivities are not the same. If I knew this years ago, I would have gone with all the same devices.