There is no universal preference: you probably have to weigh the formatting in context.
Some relevant discussion:
Use–mention distinction (Wikipedia):
Although the standard notation for mentioning a term in philosophy and logic is to put the term in quotation marks, issues arise when the mention is itself of a mention. Notating using italics might require a potentially infinite number of typefaces, while putting quotation marks within quotation marks may lead to ambiguity.
Quotation (Stanford Encyclopedia of Philosophy):
[...] quotation is not invariably indicated by the use of quotation marks. Sometimes, for example, italicization is used instead, as in:
Bachelor has eight letters
Other devices employed as substitutes for quotation marks include bold face, indentation, and line indentation.