"Blues" has a technical musical definition.
"Small b" blues is the more rock or country type of blues - typically done by whites. It also shows up in jazz, even big band jazz. It is usually much more arranged and processed, and therefore much cleaner sounding; but it still follows the same scale patterns and the 12 bar chord progression that defines blues. Think John Myall or Eric Clapton or the Allman Brothers.
"Captial B" Blues is sometimes called "Da Blues" and was/is typically done by African Americans. It is raw and has a LOT of emotional power (more so than the small b kind). Think Howling Wolf, Robert Townsend or BB King.
For the first 20 years or so of R&R, approx 1955 to 1975, it was understood that most R&R was actually small b blues. So the fact that something sounds more 'rock' than 'blues' means that you are not using the technical definition.