I agree with this sentiment, the size of the lens is not to be taken with a grain of salt. The 24-70 is more manageable, being a little more than 1 lb lighter and noticeably smaller. Having used the 28-70 prior to my purchase, I had an understanding of what I was getting into. I had seriously debated between the 24-70 versus going up to the 28-70, due to the size alone. The additional weight isn't much of a factor for me, however the physical size of it is a different story. For me, having one lens that will replace my 35mm 1.8 plus the other prime I would have bought, the 50 1.2, the 24-70 2.8, and
possibly the 85mm 1.2 (or 2.0), made this a no-brainer.
I have the 24-105 f4 L, which I debated whether or not to sell. I will likely end up keeping it simply for the portability factor, being almost exactly half the weight of the 28-70 and a pretty small walk-around lens, plus the extended reach on both ends.
Side note: my package/lens is out for delivery and should be here within the next two hours