[Pat Sitton]

I realize that this is an old thread but, to my surprise, the previous posters left out a vital factor.
FCPX is written to use OpenCL-based GPUs (such as AMD/Radeon) rather than CUDA-based GPUs (Nvidia).
As a result, there are many tests that show that cards like your GTX 980ti — while blazing fast for gaming and with Premiere Pro (which is optimized for CUDA GPUs) — are pokier than far cheaper OpenCL cards when used with FCPX. This is most likely why you found FCPX to be less responsive than PP. I don’t have URLs readily at hand for such tests but this is general knowledge and you should be able to find such discussions easily.

all the best,
Pat