5050/5730 designate the package size, not the performance.
Wikipedia is not an authoritative, or even good, source for technical information. And in this case, it's simply wrong. There some 5050 size LEDs which are more efficient than some 5730 size ones. e.g. the 5050 size Luxeon L150-3070502400000 produces 146 lm/w, while the 5730 size Bivar SM5730UWDW05 produces 112 lm/w. Note that both are more efficient than what the Wikipedia article says is the maximum efficiency available in either size package.