Readability Analysis

How useful are the various mechanical ways of measuring readability of a text?

Do they accurately define a text readability for all contexts?

what do the mechanical measurerments say about the comparative readability of the two texts?

Do the mechanical measurnments help to show absolute and difinitive difference between the texts?That is,do you thick everly reader of these texts wound have the same experience of their readerbility asyour personal experience?