The bracha that appears in all modern siddurim that I'm aware of for the tefilla shel rosh (whether normally or in case of interruption between the two tefillin) ends with the phrase al mitsvat tefillin (על מצות תפילין). This is also what appears in our printings of the Babylonian Talmud at Brachot 60b and Menaḥot 36a.
However, the manuscripts of Menaḥot that we have uniformly have the text b'mitsvat tefillin (במצות תפילין). See also Dikdukei Sofrim, where it's also noted that b'mitsvat is the text of Halachot Gedolot (Hilchot Tefillin), Rif (Tefillin 8a in manuscripts), HaEshkol (Vol 1 p228 ed. Albeck), HaIttur (Hilchot Tefillin Ḥelek 8), and Or Zarua (Siman 582). On top of that list, I found that Rosh (Pesachim 1:10), Rashba (Hameyuḥas leHaRamban 202), Kol Bo (146:95), Halachot Ketsuvot, and Geonic Responsa have b'mitsvat, and Rosh and Kol Bo explicitly prefer it over al mitsvat.
My question: What is the history of b'mitsvat since the end of the Rishonic era? Is there any trace remaining? Has anyone dealt (historically or halachically) with b'mitsvat vs. al mitsvat since the Rishonic era? Has anyone from any era discussed this explicitly and come down on the side of al mitsvat? (I'm not interested in a preference for al mitsvat by simply omitting b'mitsvat, eg. Rambam in Mishne Torah; I'm interested in explicit discussions of the preference.)