yes, I agree to some point. I've deliberately picked the "worst possible view on size". :-)
In front or rear view one gets a better sense, just how much smaller an A7/R is compared to even the smallest FF DSLR, even with lens mounted. Much less obtrusive too (important to me for street shooting and other situations).
Main issue are the lenses. Neither Canon nor Sony have the kind of pancakes/ultracompact lenses to go "small and light" - sole exception the EF 40/2.8 which I really like. The Sony FE 35/2.8 is ok for me sizewise, but not pricewise [not even with Zeiss written on it]. Unfortunately no wide angle pancake (e.g. 20/4) or ultra-compact tele (e.g. 85/2. on either side (yet).
I picked up a EF 28 f/2.8 IS when it went on sale for 350, and it is much smaller than my other lenses. Only had took a couple snaps to make sure that it was functioning ok and to set the AFMA roughly, but I was impressed by its compact size and IQ. Never tried the EF 40 f/2.8 but it is even smaller. So a set of compact primes (24 f/2.8 IS, 28 f/2.8 IS, 35 f/2 IS, 40) exist for the EOS system. The difference in body size is not that significant to me because it's really lens + camera that matters, and if it doesn't fit in a pocket, then I'll be bringing a camera bag anyway.
The thing that bothers me, is that the lenses being offered for the A7/A7R are slow and expensive. 35 f/2.8, 28-70 (f/4-?), 24-70 f/4, 50 f/1.8... I see the advantages for landscape users like LightandMotion, because he can get a high IQ FF sensor at a good price and does not need AF. And those that have lots of vintage glass can use them with appropriate adaptors, but how big are these market segments? The slower lenses allow them to be more compact, but restricts their use indoors in ambient light. I'd rather use a 35 f/1.4 at ISO 3200 rather than a 35 f/2.8 at ISO 12800, where noise and DR suffer significantly. And the faster the glass, the larger the lens, and the less advantage the mirrorless system has.
I'm all for mirrorless versions of the 5D, 6D, etc in due time. Without a physical shutter, the sync speed and frame rate can increase. Focus peaking will be nice but only if the EVF reaches the quality/responsiveness of the OVF. More MP in smaller packages with higher frame rates will require more processing power, and battery chemistry has not changed. It's not surprising that these mirrorless offerings have abysmal battery life' they're using the same technology as DSLRs, their batteries are smaller and the electronics are active all the time. Unfortunately, there aren't any good technologies to replace Li-ion, so the battery will need to be bigger.