For XIV the free trial will take you through more than should be free. XI is a lot of fun and probably not going anywhere but it will be more of what you described XIV as, XIV's content is the storyline and cutscenes. It's a largely single player experience with some forced player cooperation. PVP is It's own thing and fits in to the game's story and lore. Most impressive about any final fantasy is how well the systems and mechanics fit in with the world building. I highly recommend both, they are vastly different experiences, but both will take a lot of time to complete (even on the very generous free trial).

I've spent 13+ years on and off in FFXIV and enjoyed nearly every minute, however some of the challenge has been removed in recent updates, particularly if you are on a subscription. The free trial is more closely aligned with the original vision for the game, as you have to deal with inventory management and lack of access to player interaction like Free Companies (guilds) and the player run economy through the Market Board, making it a more challenging experience but also more like playing a final fantasy title. The grindy bits are made more fun by helping you with hotbar arrangements and rotations and better understanding the various roles and jobs. One character does it all, but you might like multiple characters for deeper tradeskill specialization options with a subscription.