Thank you.
I asked on Facebook (better this way, by mail i was not having answers). They give me some clues:
"The studio line has some upgraded components and is built a bit different. They have three bores instead of 2 which decreases intermod distortion for a bit of a cleaner, clearer sound. The cables are also a custom made premium copper cable that has a bit of a better sound quality.
The studio line is not designed for stage use per se, where the others are made to be used on stage also. They could be used on stage fine, but they are not designed for it."