Hmmm, I'm going to have to go with Tales. I used to be big on FF games, but for some reason I'm really getting turned off from them. The last FF game I really appreciated was X. Tales games I've always enjoyed, save for DotNW. I'm an fan of the older FF games really, that's one reason I'm partial to the "Tales of"series at the moment.Right now FF XIII isn't even on my radar but I'm stoked for Vesperia PS3 and Graces. Obviously, I'm not saying which one is better than the other since it's all subjective in the end, but for now I enjoy Tales more.
FF games tend to have deeper stories, but Tales games always have awesome character interaction, which is big for me. I enjoy the Tales cast more than the FF cast when it comes to that. I felt nothing for the FF XII cast and could care less what happened to them, I really tried...I at least enjoyed the gameplay enough to enjoy the game, but the cast itself bummed me out. The "Tales of" series always seems to have an enjoyable cast,(Again, with an exception of DotNW's Emil and Marta)even if they aren't the most original characters out there.
In the end, I enjoy both series for what they are, but I like Tales of more at the moment.
Also, I am sad that not much people seem have been bringing up Final Fantasy Tactics(PSone,PSP),that to me is the most
brilliant Final Fantasy out there. If you haven't played it, do yourself a favor and go get it right now. Awesome game.