It's a waste of time to learn a new version, method, what the fuck ever of UNIX.
Is it? Isn't there any value to learning Solaris if you know HPUX?

Besides, 95%+ of it is exactly the same.

All a distribution is - or should be - is a snapshot of the vast universe of UNIX software and derivatives.
Well, a segment of the vast universe of UNIX software and derivatives.

With an installer and package management system.

It's not a fucking religion! - you can't compete with vendor UNIX this way!
Debian is as easy to install as any vendor *nix that I've ever used.

Debian is as easy to maintain as any vendor *nix that I've ever used.

Debian is as stable (if you stick to stable) as any vendor *nix that I've ever used.

I want stability, I want ease of installation, I want ease of support
-and-
I want that on commodity hardware at a price I can sell to my boss.

It's not a religion.

It lets me do the work I need to do, when I need it done, and it doesn't have any nasty surprises.