I must take exception with the statement, "The problem is, F2.8 on Micro Four Thirds is equivalent to about F5.6 on full frame in terms of depth of field control and low light performance, so the 12-35mm F2.8 and Canon 24-70mm F2.8 is not really a like-for-like comparison, and a 24-70mm F5.6 for full frame would be much smaller than the Canon 24-70mm F2.8." Yes, in depth of field control. No, in low light performance. F2.8 is F2.8 on any sensor, Period, end of discussion. Some sensors do have more sensitivity to light.
http://frugalfilmmakers.com/2013/08/11/21st-century-camera/