Only disadvantage I can see on these 1.4 G lenses is the slow AFS gearbox design, so tracking and general acquiring focus is slow compared to for instance the 24-70 or 28-70 AFS 2.8
Michael has some special feature with lenses he likes, APO is one of them sharpness wide open is another, for focus stacking.
Frank stated in the other thread his 24mm 1.4 was not sharp, so must be defective.
Nano coating is really a big difference in many situations, so highly recommended IMHO.
I assume you are referring to Sigma lenses?
It is true that this is my main beef with Sigma Art series.
I concede that the Sigmas Art are sharp and even very sharp and Ughhh....that's about it.
Sigma Art lenses are unusable under certain conditions which are crucial to my type of photography.
1- Acquiring focus sucks.
2- Acquiring focus in low light.....fogetaboutit. This sucks big time.
3- I also have mega problems using Sigma Art lenses with Speedlights and Profoto. The reverse engineering of Sigma fails miserably.
Try shooting strobes in low light or any kind of light and you will walk away with disgust.
Of course, the cyberspace alleged reviewers sing songs of praise for Sigma. They do not tell you that Sigma Art is a one trick pony.