I think WFO summed it up pretty nicely.
Running it well on a PC will most likely cost a little more than a PS3, but you will probably also get better perfomance and I think there might be a few slight advantages in gameplay such as targeting with a mouse/keyboard imo which I think can play a role in PvP.
Playing XIV on PS3 will also most likely be a much better experience compared to XI on 360. I say this for several reasons with the new controller UI being point number one (and I think it is a very big one, if it is a good as it looks to be with the little info we have gotten so far) and point number two being that I can't imagine XIV being as poorly optimized for PS3 as XI is for 360. So basically if you thought 360 was okay to play on I can see PS3 being a very pleasant experience.
Overall I think like WFO said it also depends on what other things you want to do. If you prefer to game in your sofa PS3 is a cheaper and nice option, but if you want to play games and do other things on PC otherwise, of course that is a better option even if it costs a little extra.
Edited, Feb 13th 2013 12:42pm by Belcrono