My son plays both, but CoD really sucks. It is so obvious when someone is cheating.
I would imagine it takes much more work to design something skeuomorphically than it would something flat. And clarity is the top priority - you should instantly know what the thing does upon seeing it.
What matters is not hours but choice: can one choose to use her time at her own will? If she can, then I don't see any issue at all.
For input to screen latency, I think wired keyboard and mouse would be important. For "instant app opening" a recent CPU and enough RAM, and a NVME SSD. But beyond that I'm not sure. Does anybody have any recommendations or tips? Does a 140 Hz or G-Sync monitor help? Are there any pitfalls (I've heard anecdotically that some CPU power saving states can cause micro-stutter)?