Digital mode reads conductivity only (the bottom to top on smart screen), while smart find reads both conductivity as well as ferrous content. in other words a coin might read 28 on the digital and read far right on the smart screen, Now a piece of iron might also read 28 in instances but read far left on the smart screen, if in digita only they would read the same. This may not be a true example but just to let you understand what I am saying.
Also in smart find you sometimes catch an oddball reading where the curser doesnt normally fall, but sounds good.. these are usially good targets.
Main thing is learn how the audio reacts to good targets no matter what mode your in, the good thing about the smart screen if hunting mainly coins is, there are mainly only about a few spots on the smart screen where the majority of coins fall and little trash(except in the nickel range), even though there are many like digital readings on trash where coins read...