For ni200 temp control either one of these mods will serve you well. I have both and love them in both power and tc modes. It will come down to personal preference on look and feel. The Sig is built like a tank and I love the feel of it. YMMV. Enjoy your choice.
My opinion:
If you want all the latest and greatest features that may or may not work from time to time with questionable build quality, then get the X Cube.
If you want rock solid build quality and performance with no updates then get the Sig.