It depends on your needs. If you are looking solely for a digital cinema camera, and money is no object, I'd go with the Alexa. If money is an issue but extends far enough to afford a Red with the M-X sensor, then yeah, obviously as a solely digital cinema product the Red is a superior product.
If money is an object, then clearly the $5,000 AF100 will have a lot of sway over a $30k Red kit. And if you need a video camera too, the AF100 does that job.
This brings up a good point. Red is not a video camera in the conventional sense of the term although it can be used to produce video. They shoot much more like film cameras than video cameras and require a different skill set. It is a work flow that is more familiar to digital still photographers than videographers and there is a significant learning curve to get the best out of them.
Alexa is still a beta stage product and they are having some teething problems apparently, including RF shielding issues and a run in with the FCC over non-compliance with part B certification regs.