@Marshmallow – excellent topic.
It depends – the world building and its consistency as discussed here controls which I prefer:
Whichever systems are chosen, as long as the author is double checking their continuity then it will work.
The infamous failing of Skyrim’s magic system to make sense if a person with offensive magic is thrown in jail is all the more glaring, because for the most part, they do a wonderful job of keeping their continuity intact.
Katherine Kurt’s Deryni historical fantasy writing is my all-time favorite implementation.
Her world-building is very complete, given her setting, source material and subject material. She built a system which makes sense from a 10th century England perspective, then wrote it in modern day terms and framed it in concepts of our times.
Very few authors, even award-winning authors, have her ability to execute a magic system as she has, book after book.
I suggest anyone, needing a role model to follow, look into these books further.
The system I am building currently in my most “magical” project is a “hard system” that is explained and viewed through the characters’ eyes in a “soft system” manner. It is inspired by Kurtz.
The system I am writing about that is based in a Victorian Age type of world is explained in a pseudo - hard manner … much like the science of the day was. A Victorian person was more likely to see Séances performed and attribute what happened by “soft magic” terms, even as they were attempting to use the scientific methodology to test their world… this is inspired by the writers of the era.