How important is GPU acceleration in FCPX/Motion 5?

Question

So I've been using FCPX and Motion5 on an old mac (mid-2010 iMac, i3 dual core) at work (self taught - 3-6 minute promos and tutorial vids for our web services, not remaking Blue Planet or anything!), and as an Apple Convert I want to replace my home computer with a Mac, and also do some of these spots for a sports team I'm involved with - short competition reports/promo spots/review films for the Christmas party, that sort of thing. DSLR video, so nothing too taxing by industry standards - not 2K/4K, multicam, or any of that good stuff!
It seems that I can't get a new Mac Mini with discrete graphics at all, and the cheapest MBP with discrete graphics is the 15" non-retina, which is further than my budget really wants to be pushed (I could use the portability of a mini or macbook, hence the exclusion of iMacs).
Given that I'm doing relatively light work (nothing more than 6-10 minutes), would a new mac with a beefy cpu and Intel HD4000 onboard graphics (quad core mac mini for instance) manage, or should I really be hunting round for a refurb unit that perhaps has a slower cpu and is a bit older but benefits from discrete graphics?
Basically I'm asking how far I should trade off cpu vs gpu. FCPX tech specs state Intel HD 3000 as a minimum spec, and all the new units have HD 4000, so technically it'll run with onboard graphics, but I'm wondering how far it'll get before keeling over - probably not very!

Answer 1

If you want a smooth and more importantly non-lagging NLE Experience. FCPx is NOT the way to go. You could put in the fastest GPU on the planet and FCPx would still be laggy, unfortunately. At least in comparison to Premiere Pro which is very very very smooth.
I myself, NEED the "Media Openness" of FCpx. Meaning that it enables me to cut faster than any other app on the planet. However, once I try to use the features it HAS, like compositing, titling, compound clips etc etc etc, the app totally bugs down. And that regardless of GPU. All such things are done on the fly in PPRO. With NO Hickups and that is due to its architecture which is highly optimized for GPU. Alas, PPRO's media management/integration is nothing compared to that in FCPx. Which is why I use FCPx ;-)
PPRO is optimized for GPUs FCPx is NOT !
So to your question !
The only thing a faster  GPU will get you is the ability to have eye candy-stuff like "Opening of Inspector" look smooth and perhaps your event library scroll a little faster. I have 7 Macs here at this facility all ranging from Pro Graphics cards to consumer ones... There is very very little difference in actual performance.
In my own personal experience, when dealing with FCPx the GPU matters very very little. What WILL make FCPx speed up significantly is running OS X (And thus FCPx) off of an SSD drive.
Above are MY findings and NOT something I have read about nor are they based on any forum-specs.
And remember - Speed is a very relative term. The more you work and the better you get at what you do, the slower the routines appear to be. So to someone writing more than he is cutting, FPCX might be a very performance-fast app but to someone spending his whole day and night with FCPx the application is extremely laggy and slow when used to its full extents.