I have the 3.5" x-factor mid arm with the high steer kit which is now called the 3.5" max travel (http://www.rockkrawler.com/pages/catalog/index.php?r_itemID=364
). I love this setup. I was considering the 3-link rear, but I decided to wait until my factory warranty expires. I did install the rear shock relocation brackets and the rear shocks that are used on the 3-link kit because they are different than the shocks for the x-factor lift. The relocated shocks work for either lift, so it wasn't an issue even if I decided not to install the 3-link later.
The great thing about the RK stuff is that I can add the 3-link upgrade kit (http://www.rockkrawler.com/pages/cat...p?r_itemID=156
) in the future. I'll be able to keep everything that has already been installed on my JKU from the x-factor lift except that I'll need to remove two rear upper control arms. The 3-link upgrade kit replaces the two upper control arms and provides even more articulation in the rear because there is less binding.
Good Luck with your decision. You can't go wrong with either choice.