I thought about the 24-70 and that extra 4mm would not hurt me at all. I still have my PZ 16-35 as well. I thought the 24-70 is older and bigger but did not really look at that
I used the 28-70 on the A7C, A7R4, A7R5 and A74 as my EDC for hiking and travel. Loved the handling, size and the 67mm filter matched my 20G/35GM/FE85 prime kit.
I owned a bunch of Sigma primes and found the 28-70 rendering to have similar qualities which I personally liked.
My copy was soft enough @70 that I noticed it 100%. For casual travel, I was ok with the softness @70 but not for landscapes.
That was one downside for me and it might be attributed to manufacturing variation. The other is that I prefer 24 vs 28 at the wide end.
I really like this lens. Its my favorite zoom lens. I previously had the tamron 17-28mm but I found it sharp but flat and boring. The Sigma has a similar rendering to the 45, 23 F3.5 and 90mm lenses. The center is sharp at all apertures. Its weaker at the long end as has been mentioned but lends a dreamy look to close up head and shoulder up portraits. I believe the tamron 28-75mm G2 might edge this lens optically in terms of sharpness (particularly corner and at longer focal ranges), but i prefer the bokeh and overall rendering of this sigma even over its 24-70 sigma counterpart.
