If we're just talking reputation
it might have helped his reputation with certain types of music geeks (like most people here) but with the general public I think he'd have ended up as a cult figure. People will still know Layla (although I think it would not be AS popular with the continued momentum of his solo career, which produced numerous albums that outsold the Dominoes album) and the Cream songs that everybody knows, but not nearly as many people would know the guitarists name. I think even Duane Allman would be a bigger name because his name was in the band's name. Clapton would only have one album with his name on it and that's the 1970 solo album with After Midnight, Blues Power, and Let It Rain on it. That's really the same band as Layla, for anyone who didn't realize that and might possible care.
If Clapton and Carlos Santana had both died at age 27 I think more people would know Carlos Santana by name.