I will say not a must ,

Try side by side comparison of Nexus S and One X

opening app drawer - same
loading gallery - one X faster a bit ( 0.5 sec i believe)
scrolling the menu - smooth , both no lag.
never try much ,

mind you this is single core vs One X . One X for sure will faster than the Nexus S , but not much. maybe it will shine in latest games . normal using single core still fine, thanks to the Jellybean update on the nexus s .