As Data Transformations are case sensitive, using the Text Casing settings will affect your Data Transformations. For example, let's work with a constituent attribute that tracks a Favorite Baseball team and links to a table of team names.
In our sample situation, let's say that we have the following table entries available as choices for a Favorite Baseball team:
If our text casing is set to No Casing, we will see an exception for the value of 'CUBS' as this does not match the text set up in the From Source column of the Data Transformation:
If we set our text casing to Proper Casing, then our Data Transformation will process correctly for the same value of 'CUBS' and the field will import into Raiser's Edge as 'Chicago Cubs'.
For more information regarding how different settings affect data transformations, see this Knowledgebase article.