Overall there is not much difference. Especially once if you shoot at F8 for trave a lot.
The Sony 24-105 f4 also got sonys new hybrid IS update, which means the IS works in tandem with IBIS on the A7R V and newer, making it probably Sonys best stabilized lens. Max magnification is also similar.
This brings the only differnces down to weight, range and aperture ring.
I sold my 24-105 to fund the 20-70, which balances better on the a7C2 & gives me about all the very wide FL I need for interior shots. For the longer range landscape to 200mm I use the Tamron 28-200. The kit 28-60 is also fine for street at f/8
Resurrecting an old thread, as I have become recently interested in the 20-70 lens, mainly for the weight and form factor (great for travel).
Currently my main wide-to-normal kit is:
16-35 f/4
24-105 f/4
20 f/1.8 for low light and astro
I also feel that the 24-105 f/4 is somewhat unfairly maligned. It has a very useful range (24mm is what I would consider to be truly "wide angle", 28mm, not so much) and is sharp enough for general travel purposes. Paired with the 16-35 f/4, this combo gives a wonderful focal length coverage.
However, if one wants to have a one lens kit, the 20-70 f/4 is a much better choice. It basically straddles in the middle of the 16-105 range (arguable the most useful range). One may need to toss in a fixed focal length ultra wide to cover the wide end; I think the long end is much less significant (you can always crop).
Quite some time ago, I replaced my 24-105 with the 20-70, and haven't looked back. This is on my A7CR. Most days, the 20-70 is the only lens I head out with
My standard travel kit is the 20-70 accompanied by the 16-35 PZ f4. I prefer the lighter weight of the wider lens, when I feel access only up to 52mm is sufficient.
I'd love to see something like a 20-70 PZ, assuming that the architecture would result in further reduction of weight.
The 24-105 was an excellent lens that served me well for a number of years - photos here: https://flic.kr/s/aHsmegn6Dk
I have the 20-70/4 now, which seems a bit sharper to me, but I miss the longer reach of the 24-120. Sony 20-70 shots here: https://flic.kr/s/aHBqjABJaK
I've been playing with the Sigma 20-200, but it is not good enough to replace my 20-70. I would love for Sony to produce an excellent 20-120 or 24-200.
