100% vs 60% CPU

With my friend Tommy on the island of Gotland I did some test when we were having hangout (video call).
I have been quite concerned about the CPU-use when I use the Hangout plug-in. It often goes up to 100%
Our simple tests were done when I switched between Chrome and Firefox.

 

• When I used Chrome CPU-useage was about 90%.
  No difference when I deactivated all plug-ins

• When Firefox was used as "frontend", the CPU dropped to about 60%.

 I believe I heard a rumour that even Google recommended the use of Firefox when doing a hangout!
 I would welcome views on this comparison. If you want another "front-end" videoprogram like Wirecast, XSplit or the Open Broadcaster Software you definitely need that extra CPU%.