Maybe it's because I came into HW later (either just before or just after 3.3), but I felt Stormblood's story was superior. I loved all the dragon history, and the war between them and Ishgard, but with how epic the end of ARR was, felt like they pinned themselves in a corner with HW's story taking up so much space that the parts that were call backs to finding your companions/Ascians/etc didn't pace very well. Stormblood on the other hand is back to the more overarching story, and the pacing for how you go through it is fantastic. I thought HW's picked up right at the very end, but maybe if they had done all through 3.3 the Dragon war stuff, then after it was settled gotten back to the main story elements. They sort of did that with 3.4 and 3.5, but all the random interludes before that made it feel disjointed.
As for gameplay changes, Bard is fucking fun as shit to play. Love dropping the bowmage shit, and the way they handled the songs now is great. A lot of weird utility in a way with so many different things we can cast on other party members, but makes sense for the lore of the class I guess.
I feel like they have plenty of options where to go from here too for upcoming patches in SB...even though a bunch of loose ends were tied up already.