The same information gets shared and the same decisions are reached over the conference call as they would have been face to face.
Which is to say: none.
Personally, I find an email thread 100 times more useful. For one thing, it gives people an opportunity to formulate an idea rather than just blurting out the first thing that pops into their heads.
Sometimes, that's true, but not always. I was part of a conference call last week, which was very useful -- far more so than the corresponding email thread. We needed resolution on something, and it was dragging out forever via email. A 45 minute conference call took care of it, and everyone was clear on what was going on. And, for what it's worth, it also involved a significant amount of brainstorming, and blurting out the first thing that popped into our heads.
In fact, that was one of the reasons why an email thread was so useless -- someone on one end would spend a long time crafting a reply with their idea, which had a hole glaringly obvious to the person on the other end. But it would take a few days to get a reply, along with another idea. Lather, rinse, repeat.
Sometimes, an honest to goodness conversation is just plain better than email.
If nothing comes from a meeting, then the person running the meeting didn't do their job correctly. (And yeah, I've been that guy, sometimes.)