It's really quite simple.
"Essential" is the peasant tier. You get what breadcrumbs the nobility is willing to drop for mere mortals to chew on. May be good, but generally not. Also required for online if you're so inclined.
"Extra" is the "definitely not Gamepass" tier. So, no first-party titles at launch, but genuinely good stuff and also some indies day one (like Stray).
"Premium" is the "I have more money than sense" tier, that includes some additional titles (like up until recently GTA Vice City Definitive Edition, which was absolute dogshit), also classic games with terrible emulation and game streaming (aka PSNow).
So basically. Get "Essential" if you really want online/a few games per month, but nothing else. Get "Extra" for better value. Get "Premium" if you really have too much disposable income.
(And for full disclosure, I have Premium currently, but that's just because I didn't remember to cancel it before renewal. Next year, I totally will. Or I'll forget again.)