Bass, Frequency response, Etc...Noob Question

Sorry if this has been covered before, but I looked through a bunch of pages and didn't really find exactly what I'm looking for. I'm confused by many of the spec numbers provided by manufacturers with regard to bass and frequency response and how these numbers relate to real world listening. I'm mainly talking about the bass end of the spectrum here...For example, a speaker manufacturer lists a frequency response of their speaker to be 35Hz-20kHz +/-3db, which while, not quite full range, appears to provide a nice amount of bass (I know there's a LOT more to this such as room size, placement, etc, just bear with me). My confusion comes in when writers or reviewers state that a speaker with the above specs to be better suited for vocals or jazz, and not meant to "rock", while a speaker with similar specs (sometimes even not as low on the bass freq) might be recommended for rock. What makes one speaker more suited for a specific type of music than another? Is it the "oomph" and controlled power of the bass frequencies? I'm just curious as I've seen speakers that I'd consider checking out, only to read or hear that they are not suited to "rock" music (my primary listening). I know this is very vague, and I'm unable to properly articulate what I'm trying to get at (sorry it's late). I guess a quick example would be why a speaker like the Reference 3a De Capo is not as suited to rock music as say a Klipsch Heresy might be...Any help would be appreciated!