To the eye, not really a lot. Once you move from 24fps (film) to 60fps, there is a HUGE pop in perceived motion. The jump to 120 from 24/30 (actually 23.97/24.97 and what most content is broadcast at), is even more significant. Thanks to MUCH research in VR the last few years, we know that 90fps is where the brain is willing to believe motion is real (24 is actually just the least we need to see motion and not flicker) so anything beyond is really just marketing gimmick to 99.99% of the population (and the other 0.01% are likely fooling themselves). In fact, most sets use a technique called strobing for anything over 120Hz.
The other side of the coin is that the added frames are interpolated (fake; created by analyzing adjacent frames) and they aren't always what you'd hope for. When they're wrong, they're VERY wrong and the only way to reduce the error is to sample more frames. To do this, instead of showing you a frame, the TV must hold onto it, receive a 2nd (or more), analyze them, THEN display the 1st, the interpolated frame (or frames), then the 2nd. This adds latency that you might notice even with just software interfaces and SURELY if you're a gamer.
Some folks just don't like the effect after a life of watching 24p content.