I would say FFXI is better right now but FFXIV is new and has a lot more potential than FFXI had. FFXIV is the same as FFXI in the sense that it's not your typical MMORPG, if you go in expecting a wow competitor then you'll be disappointed. The game plays like a console RPG similarly to FFXI and everything isn't simply handed to you with nerf patches and tutorials for every bit of the game. You'll find a lot of similar concepts they used from FFXI but at this point it's sort of hard to make a comparison because FFXIV severely lacks content right now, if you want to try it before buying it you can try and get a buddy pass from someone that bought the Collector's Edition.
In terms of gameplay/story the only similarity between the two is the races. The world, the combat system, the storyline, the crafting, everything is a lot different.