Conclusion

After performing the tests, the initially asked questions can now be answered.

How good is the Windows 7 Defragmenter actually?

The Windows 7 Defragmenter does quite a decent job. Unlike its Windows XP counterpart, it does not perform as well at the boot optimization, but scores in the disciplines defragmentation and consolidation of free space. Thus, the Windows 7 Defragmenter is competitive with the other defragmenters. In other words, other defragmenters are struggling to make the system noticeably faster. An advantage of the Windows 7 Defragmenter is that it automatically works in the background. The user does not need to worry about anything in that regard.

Which defragmenter is the best?

It is difficult to determine a winner for this test, as there are hardly any differences between the defragmenters. Significant differences can be observed only for the boot time and Civilization IV. Therefore, this is more of a list of "defragmenters that are only a little better than the Windows 7 Defragmenter":

1. MyDefrag 4.3.1
   Although MyDefrag 4 is now over 4 years old, it performed better than any other defragmenter.
2. O&O Defrag Pro 16, 17 & Free 14
   In this test, too, O&O Defrag performs almost as well as MyDefrag 4. This applies to both the paid (Pro), as well as for the free version. The former provided slightly better results with the Optimize/Complete method, though. The latter one, on the other hand, created a striking number of gaps between the files, but they also had little effect on the performance.
   Update 1.2: With the new version 17 there were no changes in performance.
3. Update 1.1: PuranDefrag 7.6 & Auslogics Disk Defrag Pro 4.2.2 & WarpDisk 1.3.21
   These defragmenters could break away from the Windows 7 Defragmenter, but not significantly.
   Update 1.2: Although WarpDisk's boot optimization is even slightly better than that of MyDefrag 4, the optimization of the overall system, unfortunately, falls by the wayside.
4. Windows 7 Defragmenter
   Since no other (so far tested) defragmenter showed better results, this one gets the 4th place. It gets bonus points for the easy installation (there is none) and automatic defragmentation in the background.

The other defragmenters provided neither significantly better nor worse results. However, Diskeeper 12 can be found quite often behind the Windows 7 Defragmenter. Also, its "IntelliWrite" function has provided significantly better results in Windows XP.

Update 1.1: Raxco PerfectDisk Home 12.5 also showed weaknesses in optimization, but it clearly scores with "OptiWrite". But in return comes with a significant reduction in write speed.

Update 1.2: IObit Smart Defrag 3 also showed it's bad side as it delayed the startup process considerably and thus occupies the last place in the overall score.

The SSD

Actually, the SSD deserved the 1st place. But since it is not a defragmenter, it is therefore excluded from the rankings. Given the noticeable performance increase of 100% for some individual applications, one should seriously consider buying a SSD.

Further observations

How well a defragmenter can optimize the system depends not only on the "intelligence" of the defragmenter, but also on the application that is to be optimized. For example, Gimp showed hardly any improvement in the loading time while Eclipse started almost twice as fast after a defragmentaion.

Since the Windows 7 Defragmenter can defragment the MFT, it was not necessary to test whether or not the other defragmenters could do this.

As always, comments and criticism of the test setup, execution, etc. are encouraged and can be posted in the Forum.