what do you mean 'only a 120hz'
your eye refreshes at what? 24hz? tv is beamed to you at 30hz. 60hz will just show you the same thing twice, 120hz is exceptional, 240hz is just an extra 100-400$ to say "yeah but its 240hz, latest greatest". the human eye cant see 240 frames/sec, it sees at 24 frames/sec
corrections: your eye refreshes much higher than that and sees higher than 24 'fps' even though explaining how we see with frames per second is loaded in itself, but what i mean is your eyes perceive fluid motion anything higher than 24fps. basically what im saying is 240hz is overkill, i dont think the human eye can discern the difference between 120hz and 240hz... unless you had some kind of specially made motion blur test material and then the difference wouldnt be worth the extra dough