Lens suggestion for speakers at conferences

Pepege wrote:

(...)

I have though of the following two lenses:

• Canon EF-S 17-55mm 2.8 IS USM
• Canon EF 70-200mm 4.0 L IS USM

I have these lenses and they are very fine lenses indeed. I prefer the 70-200 most of the time, but that has to do with taste.

I'm not too sure about video. I don't do video. Once I did a test video with the 70-200 and the sound of the IS was way to loud to be useful. You'll need an external mic for that. Or a tripod and switching IS off.

The IS and AF of both are good. But they add to your skills of holding the camera to reduce camera shake. I have some nice shots at 1/20 at 200mm, tack sharp, but where the subject was capable of making large movements creating useless photos. Peter Kwok adressed this.

Or would you recommend the Canon EF 70-200mm 2.8 L IS II USM instead? It is definitely more versatile, but quite expensive and heavy compared to the others...

Well that is a fine lens indeed!
What it adds -compared to the f/4- is shallow DOF and a whole stop of light.
The costs -apart from money- are weight and size. Not always a problem, but it might be intrusive and it might be troublesome to use for a longer period of time, like holding it up without monopod for 10 minutes.

Aditional:

I'd shoot RAW to be able to restore some Powerpoint imaging in post processing.

If you're going to be at different places with different light, be early and do something with a grey card to have the WB okay.