Whichever the band does best.

If you always go out with the same caller then you know that x tune works with y dance. Since I go out with several bands who have other callers I have 2 ways of working. If they have a tune book I thumb through and see if I can pick out one that fits my dance. If not I say what sort of tune I want, maybe mention or hum one that works, and let them choose one that suits.

If bands field substitutes then a tunebook might be useful.