A while ago I found a looping example on this site (can no longer find it) that had me create a collection for each field. The collections were then stored in a variable (such as text or integer, etc.) via a Collection Operation. Once the Collection Operation is complete I did a build string along with other processes using the various variables.
Last week Cassy Freeman opened my eyes to using only 1 collection variable. See Site Workflow - Document Review Date Approaching Reminders
Thus, my question is when do you set a collection for each field vs. using the Cassy method (set a collection for 1 field - the ID and then create a query that joins the ID from the For Each against all the ID's pulled from the query filter. It seems like the non-Cassy Method creates a lot of overhead ?