I'm thinking that for most people money will decide for them.
a.)Already have a PC that can play it decently.
b.)PC not good enough, but they already have a PS3.
c.)PC not good enough, but can afford a PS3.
d.)PC not good enough, but they can afford a new PC.
There are other threads that are trying to put a solid Dollar amount on a PC that can run FXIV decently. The lowest I've seen is $500 and that is a build-it-yourself. Pre-packaged PC deals that can run this are somewhere in the ~$800 range at minimum.
e.)PC not good enough, but they can afford to upgrade it. (This is a questionable strategy.)
f.)PC is good enough, but they just prefer console.
Good question, though - Anyone that planned to play on PS3 going to run out to buy a PC for +240 resolution?
I think setting and preference enter into it as well. I personally prefer my computer room as it has a recliner, AC right next to me, TV to the left and second computer to the right of my main system, plus my fiancee's computer is about 6 feet away and we're both planning to play together.
Even if I had a PS3, it wouldn't be an option because my couch isn't as nice, we can't play in the same room, the AC is much farther away. I prefer keyboard/mouse to controller but since you can use them on either system, that's moot. For me, it's all a matter of wanting to be able to sit in the same room together, comfortably, and have my game, my TV, my reference computer, my comfy chair, my ottoman, and my soon to be wife.
Plus, money can have relative value in addition to absolute value. I wouldn't think twice about dropping 500-700 on computer parts, but 300 for a console gives me pause.