Here we tend to pronounce X like Ks so for me the two spellings are interchangeable just the X one will bring less corrections. Since I live in a place where names are read as they are wrote and there are default spellings, it might be easier for me to know what will be simpler. Like I know Sofia will be assumed instead of Sophia and I would need to say “Sofia with ph”. I have control more or less of the situation.
One of my first criterias is to be the less need for spelling or correction as possible lol because I know how complicated it gets to have your name wrong all the time.
same