DX10 and 11 will help a lot in performance and can use some of the nice things both have

Water in DX10/11 is amazing.....as particle effects , and shadows, seriusly is like night and day both in performance and quality.

No1 that plays FFXI use Wxp , and no1 that plays FFXIV uses a Dx9 card , (no supported)

the question here is why FFXIV is based around DX9 ....