some clips on youtube compare duane and carlos santana and i have to say carlos is right there with him but then carlos must have been heavily influenced by duane.
I don't think they sounded very similar in their early days. A lot of people were influenced by both of them so it stands to reason that they would have picked up on each other's sound.
Of course sheer virtuosity is not what makes music enjoyable, but Santana really doesn't have a lot of chops. He has a very narrow style and a lot of guitarists, even non-career musicians, imitate it perfectly. In Mexico it's practically a genre unto itself. Deedle-deedle-deedle-deedle-deedle-deedle up around that very high G.
I think both Santana and Allman are in the same category as George Harrison, Pete Townsend, Keith Richards, David Gilmour, Frank Zappa, Tom Verlaine, etc. They make wonderful music but they're not virtuosos of their instrument. They're not in the same league as Jimi Hendrix, Robin Trower, Adrian Gurvitz, Jimmy Page, Eddie Van Halen, Tom Morello, Yngvie Malmsteen, Joe Satriani and all the other guys who can set a guitar on fire and make it jump through a hoop.