The Stack does not include spacers, so to answer your question, reach is slightly more important as stem length can change how the bike feel.
Most bike usually come with around 25mm of spacers minimum, so a bike with a stack of 640mm would be 665mm with spacers (give or take).
Good stuff - confirmed my thoughts.
@Gndlf started
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The Stack does not include spacers, so to answer your question, reach is slightly more important as stem length can change how the bike feel.
Most bike usually come with around 25mm of spacers minimum, so a bike with a stack of 640mm would be 665mm with spacers (give or take).