I've seen the guides that list out a bunch of gear where it seems every single piece comes from some entirely different content. Ok, that's BiS, I get it...

But when looking at which i119 set to start with... well, what armor should I start with? This doesn't seem to be something that job guides really touch on.

I'm not asking for a specific job because I'm not sure what job I want to take to 119 yet - but I'd like to know how to evaluate which 119 set to use as a foundation. AF/relic/empyrean reforged+1 sets, for example, all seem to be pretty similar with only minor differences... but which of those minor differences tend to be important?