DVCpro50, but only i you´re sure no one will need a HD version in 6 months...
Also, I´d shoot progressive and If you have enough light, you can also try a higher shutter speed to increase sharpness and decrease motionblur (if there´ll be any at all with the talking heads...)
Also use the least amount of in-camera sharpening you can live with, you can always add that in post, but it will help with the edges...
Good luck!