24-105L is my go-to lens for travel, though I could choose from key primes/tele zooms. It is by no means a "small" lens but I usually fall back on it when I carry just a single lens. It is a versatile, reliable performer.
+1 for that. I now find the shorty forty a very easy addition to throw in there, too, giving a nice option for lower light work.
+1 - that's exactly what I'm doing
when I'm out on the off chance. 24-105 on camera, 40 in pocket.
With regard to the 24-70 f4, it must be intended to have significantly higher IQ than the 24-105 otherwise I cannot see any logical reason for it. Time will tell.