SB800/PW user, should I add a 910 or 700

I have 3 SB800 and got the PW with AC zone controller. I want to add another flash.

Should I add a SB910 or SB700? I was thinking I may start usind the NIKON CLS instead of the PWs? Any suggestions?

A few things I like on the SB910:
Better button layout, menu system,
Color Gels
200mm zoom

Thanks
--
Murat