Which would be the better broadening assignment, AIT instructor or ALC instructor?

I would say AIT Instructor. It's awesome training young new soldiers. In my opinion it goes Drill Sergeant, AIT Instructor, then NCOES Instructor.

For us, there is not difference (minus the ncoer bullets) as whether you teach -10 levels, or teach ALC, you are still an Instructor/Writer.

For better advancement in your career go ALC,because your dealing with NCO's and more Mature and Professional NCO's. The AIT is dealing with lower Enlisted and U.S ARMY is getting ready to have DS back with AIT,so you could be caught up in the change over.Most Careers were ruined at the AIT Level due to Fraterzation between lower Enlisted and NCO's.

My opinion is ALC Instructor for technical proficiency.
However, if you want Soldiers then chose AIT instructor. It will reflect on your leadership skills as well as WTT.

I taught at AIT and made E-7 list on my first look, with my SGL at ALC on the same board. My opinion, both assignments will help you but I think AIT is more challenging than teaching grown folks and I would take what's more challenging.

ALC instructor

I am pretty much under the idea that you should try for both. Depending on which one you get, you will still be able to shape the minds of Soldiers and Leaders. Either way you can affect change.

I strongly believe that instructing NCOES is the better choice to make. Especially since you are a Staff Sergeant. Teaching that will greatly improve your leadership and communication skills. I taught both and I had a lot more success training that course.

I feel like the weight positions like this hold kind of ebb and flow. Just like it used to be seen that being an EOL was great for promotion, and then it transitioned to MRT and SHARP. Drill Sergeant and AIT PSG have always generally been good for promotion, but lately I've seen NCOES SGLs getting promoted like wildfire. My SGL in ALC in 2012 was a SSG. He just made the MSG list last month, along with another former SSG SGL from the same course. I think the level of responsibility is higher as an NCOES instructor because you are training NCOs that train Soldiers.

I would say the ALC Instructor. That is just my opinion.