Steampunk Viking said:
Tough choice, both very good games in my opinion. It depends on what you want really, Dragon Age is miles better on a PC, is constantly getting downloadable/new content and is very non-linear with great characters and an even greater degree of customisation.
On the other hand, Final Fantasy XIII is faster paced, exillerating and has a much better overall storyline with incredibly memorable characters that take slightly longer to get to like than Dragon Age. The main problem lays with how long you have to play it before it starts getting good.
So yeah, there are the good, the bad and the ugly in a nutshell for you, well, for my two cents anyways. Hope this helps you choose. Both games are really worth checking out though.
The chief criticisms I have heard regarding FF13 are (in no particular order):
I don't care about the characters
I have heard this exact story in previous titles
The system has been streamlined
The game takes ages to actually start being "good" (as in, many, many hours)
When the game becomes "good" for many it isn't "good enough"
The combat is "different"
Some of these strike me as meaningless complaints (combat being different for example), but some of the rest are violations of central principles of the JRPG.
That said, criticisms that are (regularly) leveraged against DA:O are:
It looks like ass (on a console)
It is difficult to control (on a console)
The game will happily murder your party (any system)
Combat is a "chore" (I personally enjoyed it)
There are obviously varying opinions on things like characters and storyline etc.
For my money, I'd say the question is what sort of systems one prefers. From what I hear, the plot and characters are fairly stock for Final Fantasy so there will be no real surprises there. The key distinctions between the two lie in the actual combat mechanics (in one case a game based on position and real time interaction and inventory and skill management, in the other a more or less turn based affair with primarily skill/spell management as the rest was apparently shelved) and the overarching metagame bits (dialogue trees versus cutscenes for example). DA:O is an excellent example of a "classic" style western RPG, and for those who like games like Baldur's Gate or Icewind Dale (or any games of similar style) DA:O is a viable choice.
For gamers who favor the JRPG approach to the genre, FF13 is probably the better choice. I speak as a fan of Western RPGs, and thus I am easily swayed by bad news regarding a game I was only mildy interested in.