Barleywine
To slightly mangle a metaphor, it seems like the difference between "inductive" (bottom-up) reading starting with the particulars and working up to a broader conclusion, and "deductive" (top-down) reading which starts with a "big picture" premise and then fills in the details. Turning the cards over singly and reading them one at a time would be "inductive," while turning them all over and looking at the whole spread right away for a main theme would support a "deductive" approach. It seems to me that deductive reading would be more efficient and conserving of time; think "cut right to the chase." However, I only use it if something really grabs my attention immediately. If the spread has an even "tone" to it (such as no major arcana and few court card), I start at the beginning after looking briefly at any overall signatures (like an abundance or deficiency of something).
