Until you need them, none. They sort of become self evident and you'll know when you're in the market for them. For now, don't waste time on premature optimization.
And now you read the release notes with dread as you witness more and more functionality being dropped because they choose not to maintain it. Luckily there is FreeBSD
Best of the bad options doesn't make it a good option. It's far from reliable and one of the most common reasons I encounter for deadlocked Linux systems. Well, to be fair, it also hangs a fair share of BSDs and sometimes even a Solaris. If at all possible, I'd suggest avoiding it.