So funny how contentious certain unexpected areas can be with our hobby! I’ve seen more than a few smart people all with strong points (at least to a layman like me) pointing to why lower gauge is better, or not. And, it’s amusing how ridiculous each side thinks the other is being!
In my case it doesn’t really matter as my electrician will install 10AWG no problem. Again, a no brainer for the few extra bucks.
Also, you are not quite right on amplifiers not drawing more than 15A, when talking about instantaneous, or sometimes referred to as “peak” current.