Which is the most accepted measure for an individual's academic productivity?
There is no accepted numerical measure for an individual's academic productivity.  The available measures can sometimes be useful, but they all have serious weaknesses and many detractors.  In particular, there is no widely accepted or safe choice: if you make any public use of a productivity measure, many people will react angrily, no matter which measure you choose (and their anger may well be justified).

Added in edit:  In my experience, citation and publication counts are sometimes mentioned in letters of recommendation, but just as a crude numerical measure, rather than with any serious importance attached to them; most letters do not mention them.  (I've never seen an h-index mentioned in a letter or job application, but perhaps it is more common in physics.)  Hiring committee members occasionally impose minimal numerical standards, but just to rule out inappropriate cases ("we won't consider anyone for a tenure-track job unless they have at least two publications", say).  In the departments I'm familiar with, nobody uses them to choose between serious candidates.  Like Dan C says, they just aren't that useful: they add a small amount of information, with a lot of noise and even systematic bias.