There are thousands of manuscripts of the Hebrew OT. We have reasonably precise numbers for the manuscripts of the Greek NT, but does anyone know about manuscripts of the Hebrew OT? Does anyone even care?
There are a few reasons why so little has been done with the vast number of medieval Hebrew manuscripts. The OT is longer than the NT and 'collation' for a Masoretic manuscript involves not only collating letters, but also vowels, accents and of course the masoroth.
A further reason why no one seems bothered about collating the medieval mss is that people are convinced that they will not find much. That's why if we want information about variations in medieval manuscripts we have to go to Kennicott and De Rossi at the end of the eighteenth century. But how about the strophe beginning with nun in the alphabetical Psalm 145 (Hebrew numbering just after v. 13)? Does an agreement here between a Hebrew ms and the Greek Psalter not suggest that the Hebrew ms in question deserves more investigation?
Given the mass of Hebrew material I think that the only way to begin to make sense of it is to start devising a set of Teststellen—places where we dip in to the manuscript tradition to try to get a sense of what is worth further exploration.