Interesting question, I thank the gods of music it's only hypothetical. The respective contributions of each band are so different, it's hard for me to compare them. The Beatles seem to have had huge influence on the mainstream of popular songcraft, much deeper than the Stones. That said, my personal tastes greatly incline me towards respecting the Stones musical legacy. They assimilated and reinterpreted the gritty and raw aspects of the blues and R&B with vastly more authentic passion to my ears. The only white guys to ever play guitar as funky and with as much groove as Keith I can think of offhand are Stevie Ray and maybe Steve Cropper. Keith's style is rather low key though, he often says that he doesn't think in terms of lead or rhythm guitar, it's all groove in service of the song. The tag of being followers is a misnomer, they took longer to develop into their prime. They didn't do most of their best work until the Beatles has ceased to exist. Sure "Satanic Majesties" and some of their neodisco stuff smelled to death of trend following, but that doesn't negate their other contributions. I can't imagine the history of rock without "Satisfaction" or "Yesterday." In the end, each bands' respective contributions appeal to rather opposite poles of personalities and musical tastes. What a poorer musical legacy we'd have lacking either.
