The carbon crux is indeed a tricross. Not that that is a bad thing per se, just ride them both and see which you prefer. The Alu version should feel snappier and more aggressive, while the carbon version should be a tad lighter, and more forgiving if you try to overcorrect. Also, due to the longer chainstays the carbon version will likely handle better at higher speeds, while the alu version should handle better at lower speeds (and probably climb better).
Both are good options. Get the one that fits your riding style better.