the armors are interchangeble there's like 20 or so throught the whole game. And Likely more through DLC. (bleh on DLC).
http://www.novacrystallis.com/?p=3897.
I like the defaults of FFXIII and FFXIII-2 more. But I still like it.
But, I like having 20 outfits more than one set one. I've thought Final Fantasy and every RPG in general should have this for a long time. Xenoblade had it, Resonance of Fate had it, Final Fantasy X-2 sort of had it (in battles atleast). Final Fantasy XIII-2 had it if you paid for it. JRPG's have ignored this a bit too much.