In my opinion, I think I can easily say his is a better system, in general, however, performance in games is generally dependent on how good the graphics card is, rather than the CPU. So, your system
should performance way better in games than his.
The FX-4300 is a lower end CPU that will hold back the GPU, since the GPU is going to be a lot faster; the GTX 980's
potential is dependent on how good the rest of the system is; this is called
bottlenecking. In your case, I would suggest upgrading your CPU, so that it will not hold back your graphics card.
Depending on how much your CPU is holding back your GTX 980, your gaming performance
might not be much better than his.
The debate can be settled easily, though, by benchmarking your systems. You can either see who has the higher FPS in the same game, or use a benchmarking program like
PassMark's free "performance test."