Gents you have dipped into one of the endlessly explored topics of audio. So far as I know there has never been any definitive answer to these questions. There are answers in measurements and they are real and there are answers in simply just listening and they are just as real.
Unless you are choosing among amps that are just plain really bad, the choice often comes down to what you like to hear and what you CAN hear.
In general, it seems to me that if you like the sound then whatever you're listening too is right for you until you find something that you like better. Measurements, reviews by others, etc.can point you in a direction you might want to go in, but ultimately, it comes down to what you like in the context of what you can afford (the trade-off that we all have to make, or at least most of us).