Extra Pro features that are not in the Standard edition:

• Batch editing with the Edit Multiple feature:
  Save time by editing multiple items in batch, e.g. to fill in a field value for many items in one go.
• Customizable pre-sets for sorting, columns and folders:
  Create your own pre-set field combination for sorting and columns. Define your own folder options, even multi-level folder combinations.
• User Defined Fields:
  Create your own fields (text, number, pick list, checkbox or date) and rename pre-defined fields.
• Export features
  Export your database to a CSV or XML file.

TIP: Unsure which one to choose? Then just opt for the Standard edition.
You can always upgrade to the Pro edition later, for just the difference in price.