I hate to say it, because it promotes that whole anti-competitive behavior, but I haven't run a third party defragger since my initial testing with Vista. At the time, there were several other websites reporting that those apps made no improvement, or enhancements to the OS. I would assume the same holds true with W7. Vista and W7 are much better at self-tuning and self-maintenance.
For all the difference that third party defrager`s make it`s not worth it, Windows 7 does a good enough job for the vast majority of users, more options for Windows defrag can be found easily at the command prompt;
defrag
/A Perform analysis on the specified volumes.
/C Perform the operation on all volumes.
/E Perform the operation on all volumes except those specified.
/H Run the operation at normal priority (default is low).
/M Run the operation on each volume in parallel in the background.
/T Track an operation already in progress on the specified volume.
/U Print the progress of the operation on the screen.
/V Print verbose output containing the fragmentation statistics.
/X Perform free space consolidation on the specified volumes.
Windows 7 still accepts these Vista switches.
/R Performs partial defragmentation (default). Attempts to consolidate only fragments smaller than 64 megabytes (MB).
/W Performs full defragmentation. Attempts to consolidate all file fragments, regardless of their size.
/F Forces defragmentation of the volume when free space is low.
example; defrag C: /V /W
Personally speaking the need for third party solutions with 7 is just a myth, they may improve some aspects of the drive performance, or worse conflict with Windows own routines, and any performance increase will be imperceptible (if any at all) to the average user on a standalone machine.
Differing algorithms just give varying results this is why you will always see more fragmentation when using third party solutions. A whole industry has grown up around this subject, and let`s face it if they all reported that Windows was now doing a good enough job it would hardly be in their best interests.