"What characteristics have motivated your choice?"
Small size, the m-audio quality.

I used to mix.

SOUNDS

"The frequency curve is sufficiently neutral?"
I have not seen!

"The sound is clear and precise on the spectrum?"
Clear, too! Or maybe it is the quality of my music which is zero!

OVERALL OPINION

"How long have you use it?"
Not very long!

"Have you tried many other models before buying it?"
Not at all.

"What is so special that you like most and least?"
The integrated amp power.
Minimum: The power cable short enough, no bass boost on the v1.

Good value for money, I would do the selection.