"Usefulness" and "utility" both mean nearly the same thing.
Usefulness: the quality or fact of being useful.
Utility: the state of being useful, profitable, or beneficial
To me, the word "usefulness" sounds rather awkward and could raise doubt among some people as to if it's even a word (although it is). On the other hand, "utility" kind of has the connotations of something like a utilities service or a software utility. Of course it would make sense to reword a sentence when it sounds odd, but this questions serves a purpose when one of these two words must be used.
Is one "better" to use than the other? What is the difference between the two words? When should each be used?