Unfortunately, until I get my hands onto an actual 650w Arri light, I can't do a side by side comparison. However, I can say that because it uses the same bulbs the color temperature is very accurate and judging from my past experiences with Arri kits, the lights are almost spot on.
(Side Note: Although not the best candidate for seeing these lights in action, the lighting for this review was done with 2 of the 3 Arri lights.)