ChangeOrder:
AISC has their tables showing a bunch of common sizes for different loads and beam sizes, as DriftLimiter suggests. KootK and Sbisteel suggest a pretty common size angle L4x3x5/16 and L4x3.5x5/16 for to medium wt. framing. And, if you read btwn. the lines the longer leg is finally getting wide enough so it can be bolted to the beam and meet edge distances, etc. Much of this standardization was fabricator specific, dependant upon their means and methods of fabricating, and their approach to efficiencies of materials, their own equipment, and their labor. We kept a well stocked rack of angles for these details, and never let it run dry, because we always knew we would need clip angles. We would order that stuff by the carload, of mixed sizes. Once we had some angles out of the warehouse, for a job, and on the fab. line, our efficiency was not saving a couple pounds of angle iron, but rather not having to go back to the warehouse for another 20' angle iron just to cut a few lighter clip angles, so they all got the same size angle. Our detailers were trained to watch this stuff and detail accordingly.