I'd recommend starting with one of the 2nd style, save the 1st for later as it's really suited to long pieces. I got a 4" Kurt style knock-off and it is a perfect fit to the X3 table, with a slight modification to the supported end block you can get enough travel to mount it at the edge of the T-slots and leave you a good amount of space on the right hand side of the table. The vise I recommended I however don't like for 2 reasons - 1) The jaw opening is less than the jaw width, it's a personal thing I guess, I like to be able to rotate everything as I need to. 2) the screw is completely exposed, my vise I clamped a piece of rubber sheet to the external jaw mount position at the rear to drape over the back side of the vise and cover the exposed ways and screw.
Come to think of it, I don't see how you could swap your jaws to the exterior position for larger pieces.
I got this style vise http://cgi.ebay.com/4-Machine-Vise-w...QQcmdZViewItem