Which one is better in terms of sharpness or imagq quality? Thank you 
There is more than one 70 mm Sigma macro…
https://www.dpreview.com/products/compare/side-by-side?products=sony_50_2p8_macro&products=sigma_70_2p8_dg_macro_a&products=sigma_70_2p8_macro
The Sigma ART 70mm is amazing. I bought it and it blows away my Canon 100 2.8L.
Good article, thanks for posting. No byline so perhaps by Hamish Gill himself, though hats off to Richard Karash for the the actual testing.
The OP might like to like to see Robert O’Connor’s tests here:
https://www.closeuphotography.com/1x-test-2020
and here:
https://www.closeuphotography.com/1x-macro-lens-test-2022
I couldn’t find the 50mm on there (it might be there though) but it seems he rates the 105mm ART over the 70mm now, though both are clearly excellent.
Checking test reports can be helpful, but most of them don’t test lenses at different reproduction ratios as well as for focus shift and field curvature. While a lens might be almost perfect at 1:1, it might fall apart at 1:1.75 or because you set focus at f/2.8 and shot at f/8.
Sure, but having read Robert O’Connor’s reviews I trust him and so it does show what is possible if you don’t do either of the things that you mention, i.e. use them at a slightly different magnification or don’t allow for focus shift, and clearly the fact that he is photographing a silicon wafer ensures that he is testing for a flat field, in the same way that Richard Karash mounted his Vlads Test Target between Anti-Newton glass (that could affect ultimate resolution I suppose). I haven’t read any of Richard Karash’s reviews apart from this one because I believe that they’re on Facebook and I don’t ‘do’ Facebook.
Wow, the 105 being rated as better is amazing for the $.
Well I don’t think you should hold your 70mm ART in any less regard, I very much doubt that you’d see any difference in real world slide/negative scanning. It’s actually a little difficult to compare the results from the two different group tests but both lenses are clearly very good, I was just going on his own stated conclusions in the 2022 test.
Well, it just so happens that one of my needs for lenses is in the 100mm range to increase working distance. So the ART 105 would be great for me in comparison to my Canon 100L. So it was exciting to see that such an affordable lens is so good.
The only reason my 100L gets used is because the slide scanner I built out of a Kodak projector either has to get major reconstructive surgery to allow the use of the 70mm (the port for the projector lens is too tight for the 70mm to achieve even 1:1.7)
OR
I need to use longer focal lengths to get roughly a 30MP file after a crop (which is what my 100L produces at 1:1.65 range)
Getting to 1:1 would be great but unrealistic for me because who knows what problems chopping up the projector might cause. I rescan the selects from the bulk actions at full resolution anyways!