You must have had a different methodology for comparing photos and measuring sharpness: did you compare the sharpness at all apertures? Did you compare the center, mid zone and corners at all apertures? Under what lighting conditions did you compare the sharpness? At what distance did you compare the sharpness? macro distance, close distance, mid way distance or at infinity?
Besides, did you have a method to quantify the differences? The differences in sharpness can differ depending on the scaling method.
All of these parameters can affect the result. At the end, the Sony 90mm macro particularly shines on the A7rii sensor. The difference is less on an older lower resolution sensor such as A7r. Lenses also score lower on Canon sensors.
<div id="linkdxomark">This a comment for <a href="http://www.dxomark.com/index.php/Lenses/Sony/Sony-FE-90mm-F28-Macro-G-OSS">this page on the website</a></div>I have compared the Sony 90 mm to the Canon 100 mm (with a metabones adaptor)and also to the Sony FE 55 F1.8, mounted on my A7R and I must say they are pretty close in terms of sharpness, the 55 being a little better, which is not a surprise.
This means that the new Sony 90 mm is doing quite well but is not outstanding compared to the much older Canon prime.
The stabilization of this 90 mm is helping quite a lot for macro, but do not expect miracles knowing that the A7R body is very sensitive to any small move or shake.
This is definitly a good Sony prime.