Personally, I would buy them flat because it makes for a much lighter system. In addition, you may use a set of bindings that you may already have, or choose a binding that is different than what the integrated system offers. The Looks that come on the Dynastars are certainly a very good binding IMHO.
I do believe that there are some skis that benefit from an integrated system but generally they are narrower waisted skis designed for harder snow. I own a pair of Dynastar Contact 4x4s and find their Fluid system very heavy but I do find that the skis seem to transmit my input extremely well.