I thought I'd done a pretty good job of explaining the differences between the Blackmagic Intensity Shuttle Thuderbolt [$227], the Intensity Extreme [$284] and the Intensity Pro [$189] card the other day, but it appears not, because at least Patrick Inhofer expressed confusion about it (but then, he is getting old...)
To recap, these are capture devices that support 10 bit HD/SD with HDMI, analog component, composite and S-Video connections.
Here's another way of choosing between the three models*:
You're on your own from here...
*Of course, the Intensity Extreme could be used on an iMac and the Intensity Shuttle on a MacBook, but I'm trying to simplify things for you!