I think in general Samsung makes a better TV in terms of overall PQ than Sharp but in this specific comparison it's hard to say on specs alone. If you can get an actual Samsung (S-PVA) panel on that 75" F6300 and it doesn't suffer from significant clouding or flashlighting it could be the better buy.
120Hz usually is quite a bit better than 60Hz with motion but the difference between 120Hz and 240Hz is less significant (in general)
Also, if the Sharp uses a Sharp panel and the Samsung uses a Samsung panel, the Samsung panels are the better ones (this is based on comparing Samsungs with Sharp panels to Samsungs with Samsung panels).
One more thing is to check these in store if possible (ideally in a store with dimmer lighting) and using the picture mode/settings you might at home