I'm deciding between the 24-70mm f/2.8 or the 24-105mm IS f/4. I've been doing a lot of research and know the pros and cons of each. The general consensus is that the 24-70mm f/2.8 is better for indoor and the 24-105mm IS f/4 is better for outdoors. If I was to use the 24-105mm IS f/4 with an external flash indoors will that be sufficient? or will the 24-70mm f/2.8 still be better? I would just get the 24-70mm f/2.8 but I really want the extra focal length and IS.