Haley's musical influence is clearly in his band's arrangements, the way in which the instruments play off one another... the massive drum rolls, the sax and guitar solos each getting a spotlight. His band was really tight and they helped solidify the standard rock arrangement, but the Everly's have more overall musical influence, from their harmony, to musical experimentation, the fact they brought straight-forward country into rock in a far different way than the wilder rockabilly (and Haley's own country influences, which were a different type of country, not the Appalachian style the Everly's specialized in), to their concept album from 1958 which was a huge influence a decade later with the roots-rock, country-rock phenomonon.
Haley though has TONS of Cultural Impact, actually rivaled by only a few in all of rock history. Breaking the color line in rock for white artists, having the first rock song to top the charts, the appearance of it in Blackboard Jungle, the British tour, the rioting in Great Britain after kids saw one of those cheap rockploitation films and were chanting his songs as they caused mayhem outside theaters. He was kind of the focale point of the whole "rock is taking over the world" paranoia in 1955 and very early '56 before Presley's ascention stole the spotlight. Haley's as high as he is because he absolutely crushes in this aspect of the criteria.
Haley's musical impact though is fairly low, because while he was admired by others for breaking rock through to a wider audience, he really had such a unique niche in rock, and being older made him seem more like an anomoly to his younger peers. He was respected, but not really celebrated by his contemporaries like you'd think someone who was so instrumental in pushing rock into a bigger market would be. His slight edge over the Everly's on the U.S. charts is bolstered by his bigger edge on the U.K. Charts, so while Commercial is pretty close, it's still a win for Haley. But the real tipping point that decided it is how the Everly's were absolutely revered by other artists. Their musical impact is utterly enormous, and that along with their influence win and only being edged out slightly in Commercial Impact, means Haley's huge cultural impact can't get him past the Everly Brothers, so they win out.
Good call on asking about it though, Neg, because Haley's reputation has fallen so low over the past thirty years that most would think he's way too high and I didn't think anyone would be wondering why he was behind someone with the exalted reputation of the Everly's. Glad to see so much talk on them both.
Man I love having these discussions with you, takes me back to 02/03.
I think someone else mentioned Wynonie Harris should be on the list a while back...would you agree?