List applies the selections made the Display Options form to the data selected and then populates the Selected Data table with that formatted data. This formatting includes converting reporting units, providing Value and Flag and other features in the table. Depending on the amount of data selected, this can take time to prepare and display.
Quick List provides a basic listing of the selected data WITHOUT applying any formatting and shows the reporting units as they are stored in the Analyses table without making any unit conversions. Because Quick List does not perform any formatting or Limits, it is much faster than List and is valuable for viewing raw data.
Both can be used to create a Excel spreadsheet. When in List, click the Export To Excel button in the lower right. In Quick List, click in the upper right corner of the table to select all records and use Copy and Paste to put them into Excel. You can also copy a row or rows of records to Copy and Paste.