Here we have a majority of cognex inspection camera and irvivision on only one robot (Came with a deal when we bough the robot).
For what you want to do, inspecting a part cognex is the way to go. Fanuc IrVision is a pain to use. The user interface on the iPendant suck and good luck connecting to it via computer. The only situtation where i would go again for IrVision is for part picking since for that it's really well integrated into the robot.
Cognex have many more options and tool when it comes down to inspect parts. In-Sight explorer is a pleasure to use.