The 13″ models both Retina and non Retina options do indeed only have the HD 4000 integrated GPU rather than the additional NVidia GPU that the 15″ and 17″ models have. There is no doubt the additional GPU is going to make things run much more smoothly.
And although you only use FCP now who knows what you may do in the future as you have to figure that machine is going to last you a while.
As soon as I open FCP 7 or FCPX my MacBook Pro immediately switches to the NVidia GPU.
One point however, Avid qualify the HD4000 to run Symphony 6.5 on a MacBook Air, I know thats not quite the same but it does suggest you may have a fighting chance.
I was just trying to see if there is a preference to switch off the NVidia so I could see how it ran on just the HD4000 but sadly not an option so can’t give you a definitive answer FCP-wise.
If there is anyone here running FCP on an Air or 13″ MBP maybe they can chime in and let you know ?
best wishes
Neil
http://www.patience.tv