To make a lasting impact you need both.
There's really nothing I like about attending conferences and probably 1 in 100 speakers are both engaging and presenting something of value. The vast majority of them seem to be there to promote their latest book. Yet my employer seems to think they are important.
- The hallway track
- Having some less-distracted time around some general topic of interest
- Being made aware of things I might not have otherwise been made aware of
But, by and large, you're not IMO going to "learn about $X" by going to a breakout. It might put $X on your radar as something worth spending a day looking at.
By and large, I like (selectively) going to conferences but if someone has the mindset that they're a day of classroom-type sessions, they're probably less valuable. That's not a criticism. People just have different perspectives.