Yeah indeed, for contract customers, better go with something you're confident everybody will already know, since other people will have to manage it when you won't be there anymore.

In a previous startup I was CTO and founder for, I used a gentoo and managed everything possible by myself. This was not especially costly in time because I was already used to it and efficient, and we managed that way to stay for 3 years with 70€/mo in infrastructure cost. This has its advantages too :)