At the end of the day, I don't believe there's very much of a difference in how your DAW performs. Time taken in Gentoo, may be time taken in a different form on another distro.

From personal experience, my very first _hobby_ project before I started out in the audio industry was to set up a Linux studio environment with Gentoo. I ended up victimised and gave in to the CFLAGS club while never having gotten anything done. That was the period of my life I wish I could fix. I learned nothing except compiling. Whatever satisfaction I got was placebo, and whatever time I'd used (I won't call it "wasted") could've been for something more beneficial.

There are certain applications for source-based distros, like for eg. a server environment where your _job_ requires that you compile. Other cases are merely education-related or personal endeavour. For the few that are successfully running studios with Gentoo-based platforms, they have their reasons and it works for them. I doubt they question their own efforts and were ever in a pathetic position.