The only explanation for 3rd party companies to say things are fragmented and for windows to say they are not, Is if those companies are measuring fragmentation by a different standard. Note i said Different not better.
Only benefit Defraggler has over Windows Defrag is the added GUI options. The ability to defrag files, folders, etc. Which btw, I believe can be done using Windows Defrag via command line.
Real world performance differences between defraggler and the standard windows defrag would be miniscule. So much so benchmarking hasnt even been bothered with.
I did use defraggler in the past, and i went back to using the standard windows one after a format, I couldnt be bothered getting it and installing it. When there was zero obvious benefit.