What MechEngr said. Higher aspect ratio wings have reduced "induced" drag than shorter, fatter wings. Winglets try to mimic that effect (with varying degrees of success) due to gate dependent width limitations that Mech referenced. I've heard of zero development work that contradict that.
On the contrary, Boeing is going through considerable trouble and expense to put folding wingtips on the 777X while still allowing it to fit into the existing gate footprint.