I hardly ever call people by typing digits... I call people by selecting them from the phone book on my mobile. So it seems the most obvious choice for me would be to say "change it and replace current list with contacts". - but then, I find most of the time I call the same people. Close friends, family. It's very likely they're in the list when I open the phone app... if not, I go to contacts.

So: leave it as it is.