I think white balls are more elegant. James Bond would surely use white balls only (he used white balls in the movie Goldfinger).
For me, I can see white balls better on the fairway or rough.
However, I really like the fact that when I use yellow balls I can immediately identify my ball out of the bunch because most people I play with only use white.
When I use yellow balls it's NXT Tour S. They are very good balls and they have a very nice shade of yellow....