I don’t know why it has to be one or the other; The Beatles built on the Superstar opening of the gates that Elvis unlocked.
Elvis blew Sinatra out of the water with his hip-gyrations, rockabilly hair, and passionate incorporation of Memphis/Mississippi blues with southern country music tradition. Yep, he was in the right place at the right time, thanks be to Sam Phillips, who knew damn well what was going on. Elvis was just boy-next-door enough with his m’ams and sirs, yet had the pipes and ability to bring the force of black music to a still segregated Southern white audience. As said on this thread, that was a pretty unique thing in that day, and it really changed the musical landscape for mainstream America. Young Elvis was a force to be reckoned with, and I wonder how he would have developed without the Old School guidance of Colonel Tom Parker.
Building on that force of departure from the languid archetype of safe 50’s white social mores, the Beatles upped it by being, not a lone front singer, but a group, all attractive guys , banded together and creating new music. Elvis was not a songwriter, he was an interpreter, and melded black and white American culture into a palatable , edgey, mix. The Beatles saw, and heard that, and, as the next generation, started to write their own songs. They were in the right place, too, buoyed by the swell of baby-boomers on both sides of the Big Pond, who were ready for the , I’ll say it, tribalism of bands, as well as the cranking up of the recording industry.
Here’s a link to the Beatles/Elvis meeting, granted, an Elvis site, so probably a bit glossed.
I think Elvis was amazing in his singular stardom and change that one individual can make, musically, and probably diminished by $$$ management, and it wore his ass out. I admire him for what he did to integrate music; as a young man, he really believed in that, and got up on stage to do it, amazing energy. He busted down the doors to the mainstream audience.
The Beatles did not have to deal with the same racial strife as Elvis, and came up in a looser time, perhaps because of Elvis. Both kicked at the boundaries of safe acceptance, and we’re better for their efforts. And, yeah, I wish Buddy Holly had lived long and longer, because he would have upped the whole musical scene then by several notches.