I am very comfortable teaching. I can move about, gesticulate, draw on the board. I can see the faces of my audience clearly, and can gauge whether something is sinking in or not.
Giving talks at meetings stresses me out a fair bit, as the very act of delivering a talk is very uncomfortable. I don't really suffer from stage fright; instead, I find it's mostly the external constraints that do it for me.
First, you are always at the mercy of the organizers in terms of which computer you use. Luckily, most places nowadays you can use your laptop, but for instance people haven't been able to do that in this meeting. Secondly, the logistics of giving a typical talk is really weird -- the talks are projected onto these giant screens that are great for the audience, but the speaker stands to the side and below the screen and often sees the screen, on which he or she is supposed to point stuff, at a ridiculously low angle. Like this:
A related issue is not being able to move around. Sometimes you have to stand near a stationary microphone, as opposed to having a small mike that attaches to your clothes, so you can't really move away from the lectern; luckily, this issue is not very common. I love using the gadget that helps you remotely advance slides, and which would in principle enable you to stand wherever you like and give the talk. However, it may or may not have a very long range (the range tends to scale with price). Also, I sometimes forget to bring mine with me or to put in fresh batteries, or I simply chicken out as I get too nervous about moving around like a crazy person when everyone else stands nicely in one spot and delivers their talks.
I am also not equally comfortable pointing to stuff to my right and to my left. Or certainly not to the stuff behind my back. I remember a talk I had to give a couple of years ago, which was in this weird room with a couple of very large, nested U-shaped desks, where the audience sat. At the common opening of the U desks was the screen and the speaker literally had the screen behind him/her and could only move perpendicular to the screen, into the U. It was soooo unbelievably awkward. In order not to have your back to the screen while facing the audience, you would have to stand really, really far to the side, where people could not see you and you would be uncomfortably close to the people sitting at the ends of the U's. And this was a high-stakes talk, given to a committee that was supposed to encourage or discourage the continuation of our funding. It remains the most uncomfortable talk of my life. I don't think I did a particularly good job with the talk, and while there were other considerations (such as my collaborators insisting on me practicing in front of them way too many times before the event, which made me pissed with them because of their distrust and just sick and tired of the whole thing), the utter weirdness of the room's layout did not help. We did get the money anyway, which I suppose is what matters after all.
Lastly, when you give talks at meetings, the audience is typically in relative darkness. You sort of see the faces of the people who are not paying attention to you, as they are being lit by the laptops on which they are working instead. You have much less visibility of those who are actually listening.
Does giving talks at meetings stress you out? Do you care about the meeting room layout or other logistical aspects?