What is meant exactly by the description 'more musical'?

A good "  joke ".

R.

Work done by Daniel J. Levitin shows, "Musical activity involves nearly every region of the brain ... and nearly every neural subsystem."

@cleeds This is correct, and even more so when you're playing an instrument as opposed to simply listening to music. However the limbic system plays a major role; I had things boiled down a bit too much...

"Musical"  has different meanings to different people.

To some people, AC/DC sounds musical; others think Johnney Cash is musical; there are those who would call classical musical . . . and possibly the same applies to the quality of sound that different equipment produces. 

IMO, the term more musical refers to the overall presentation of a given work.

The pacing, smoothness, dynamics, harmonics etc. - everything one would hear with live music.  Some amplifiers may sound very quiet with no distortion, but they lack the "soul" of live music...very analytical.  Other amps sound very warm and overly smooth and veiled.

It is a rare amplifier or piece of audio gear that balances the extreme to find the nirvana which is "musical".

My summary of this thread is that the term ’musical’ is not a good term to describe sound or equipment characteristics. It appears to have multiple different means to different people.