I just don't think of realism when I think of FFXIII. I can kind of get what you're saying, but I think you're really downplaying how little that is a factor in these games.Amano's artwork has never featured very prominently in Final Fantasy characters or sprites. Mostly Amano's work is used for profiles. Final Fantasy IX was a very "anime" or cartoony Final Fantasy game with a slight realism. While the new ones almost entirely go for a realistic look with occasional popular cartoon references. While Tales games go for a cell shaded or cell shaded-like look. Amano influences are nowhere to be seen in Final Fantasy XIII at all. In fact the last time Amano aesthetics played even remotely heavily into a Final Fantasy game, was Final Fantasy VI.
Tales franchise goes for both cartoony characters and landscapes. While lately Final Fantasy has been going for realistic characters and landscapes. That's really the only difference. I do agree that many of the areas and designs in Final Fantasy games require more money and time to create, but I think that's honestly one of the failings of Final Fantasy lately. Spending money on things that don't matter like how ridiculously detailed some towns and dungeons and so forth have, while the gameplay suffers for it.
Lots of high polygon designs don't mean much if you can't interact with them. With Tales I find the ratio of stuff that is there to be interacted with as to the stuff that is simply there to look at, to be far higher in Tales than Final Fantasy. Which is better game design.
If one is arguing that Final Fantasy games are better than Tales games because they the popular cartoon style of Japan, instead of what Final Fantasy does, then that's pretty shallow. Cartoony is not worse than realistic. And I'd much rather have cartoony landscapes one can better interact with, that realistic high-polygon landscapes for show.
I'd also rather trek the cartoony landscapes of Okami than the realistic landscapes of Final Fantasy XIII anyday.
It's one of the least realistic in a way, because the gods and mythology play so much of a role in this one. XIII-2 goes even further into the fantasy and Lightning Returns looks like it follows this trend, with the whole world being swallowed by chaos and time no longer existing. I'm sure this will play into the artstyle and the world design throughout.
As far as the amount of space people can explore, I've seen tons of areas in Tales of that are as narrow as some of Final Fantasy XIII's. All of the maps in Xillia's English gameplay video today were actually very similar. Most of Ni No Kuni's are as well.
XIII-2 has a lot more open areas to explore so this is really a criticism that should be over and done with as far as I'm concerned. XIV: ARR has extremely huge areas, bigger than anything in Tales of. Pretty sure Versus will as well based on what they've said.
Does Tales of have any cities as big as Academia?