I wanted to know what the Seforim for Bnei Torah say about writing notes during a shiur.
Should one listen without writing anything and only later listen to a recorder while writing notes?
I'm unaware of specific halachic rulings or teshuvot regarding this, so this is my observation.
About thirty years ago, when I was in high school, my freshman rebbe would absolutely forbid recording him, and occasionally confiscated anyone bringing a recorder into the shiur. I will explain his thinking, later. I can't say what was done at adult shiurim, as I never really attended them at the time.
My kids recently graduated high school, and I think their yeshiva also did not allow recorders, so I don't think that attitude has changed.
I do see people bringing recorders to adult shiurim. My rav gives a bi-weekly shiur on Sefer Yeshayahu. No one I know brings a recorder, but the rav himself records his own shiur and uploads it to a web site the next day.
My take - I understand why high schools forbid recording, and, furthermore, I think adults attending shiurim should take notes rather than record. I think recorders tend to be used as a crutch to get the material and allows the listener to slack off and even fall asleep. Certainly, this is done often in High Schools, i.e. kids doze off more when they record (they may doze off, anyway, for other reasons) - at least that's what rebbes and principles have found and some have told me this. This is besides other problems that high school kids have been using their recorders for that cause other behavioral problems.
I have also found that even after I recorded a shiur, I had to write notes from the recording, anyway - esp. if I had to study for a test. So, it would have been more efficient had I written the notes in the first place. In summary, I think notes are better than recordings - it encourages better attention during the shiur, and, if you take notes as you're listening, you may write a question that pops up at the time which you'll ask the rav / rebbe then - something, I think is less likely when you passively let your recorder tape everything and you rely on listening to it afterwards. By then, you may not be able to ask your question!
In meged givas olam Rabbi Shurkin quotes reb Moshe Feinstein as saying never record a shiur! Learn HOW to listen to a shiur by listening to it live. Whatever you get, you get, and by the next days shiur hopefully your skills to listen to a shiur will have improved and you will grasp more. And so on each day.
But to answer your question, it all depends on you. Are you skilled at shorthand note taking or is it a distraction? There is no one size fits all answer. I wasted many shiurim learning the proper note taking skills, but at the same time developed a skill that helped me keep record of many other shiurim. Is that yotza schar bihefsed or yotza hefsed bischar? Tough call.