I am only using Linux on both server and client and I am happy to have a consistent development experience since 6 years.
I am interested why isnt just Apple or just FreeBSD enough for your purposes? Why do you need to use both? Just as a hobby or do both have any use special case?
Personally, I use FreeBSD for anything that's headless, and OS X is the only OS I'll touch for a desktop. FreeBSD makes for a fantastic, consistent experience for servers of all kinds, and OS X has everything I could want on a desktop. (I do still use bootcamp occasionally for games, but that is getting rarer)
I am interested why isnt just Apple or just FreeBSD enough for your purposes? Why do you need to use both? Just as a hobby or do both have any use special case?