What's the main difference to the user? Time!
EZ Notes Search can search one or more templates (and all their design elements) as fast as you can type since it relies on the Microsoft Windows search engine.
Domino Designer Search scans each design element you want to search after you specify which ones you want to search. If you start the search again, it will rescan each item again. To speed things up, the user has to spend time deciding how to restrict what will get scanned.
To illustrate the difference we did a test on a Microsoft Windows 7 Hyper-V instance with IBM Lotus Domino Designer 8.5. Our test template was the Mail85.ntf. We searched for "NamePreference". Here is the dialog which appears while the search is ongoing:
the search took 85 seconds to complete. We then searched for "LanguagePreference" and that took 85 seconds to complete as well. (Your performance may vary).
EZ Notes Search: Designer took less than 1 second to perform the search.
If you want to search more than one template, the times are additive for Domino Designer Search. So if you have two copies of mail85.ntf and want to search both at once, it would take roughly twice that amount of time. EZ Notes Search would still take on the order of a 1 second to do the search.
So if you want to quickly find something, please try EZ Notes Search: Designer: http://www.notesconnectors.com/ez-notes-search-designer-30-day-free-trial/