I don't own a CMG Reactor III, but I do own a Reactor and with 2 AA Energizer E2 lithiums it is brighter than the Inova X5T. My Reactor came directly from CMG as a replacement for a defective one I had sent back and it is very white (not the pee green color that everyone hates). CMG's customer service is great, so if there's ever a problem with your light, they'll make it right.
Contrary to ChrisM, I reserve my CMG Reactor for indoor use and carry an Inova X5T everywhere as my EDC light. The reason for this is that the CMG Reactor does not have an "off" detent, so it is very easy to activate accidentally in your pocket or pouch unless you remove the batteries first. I think CMG corrected this problem on the Reactor III, but since I don't own one, perhaps someone can chime in and confirm it.
The Inova X5T is rugged, water-resistant and has a lockout tailcap feature which prevents accidental activation while carrying it in your pocket or pouch. I personally like it because it's smaller than the CMG Reactor and easier to carry.