Ive used System Mechanic, and I must say that it does a very good job...
But Ive never used SystemWorks, so cant really say which is better.

I used System Mechanic and I wasn't impressed. Once you try TweakXP Pro nothing else comes close.

i do not use either. Both have done more bad for my system than good.

but I have tried both and if I had to choose: system mechanic.

For daily or normal use System Mechanic Pro 4 seems to be the best choice I have come across in a long time.

TweakXP works ok, but if I am going to Tweak my registry I'll take WinGuides TweakManager any day of the week, because if I am going to mess with my registry I want solid support from the programs developers, a wide base of professional IT users, message board and forums with solid on line documentation which is what one gets with WinGuides.

System Mechanic is not something I use to "tweak" my registry, it is a set of system utilities for maintaining my system so it is clean of bloating orphaned files, trash in the registry and on the drives, deleted file recovery (including email inside programs email data files (pst, and so on)) boot up program loading order and so on, it also includes other things such as a pop up stopper and virus protection...

I use the tools I find do the best job and ignore the ones that I have others of which do it much better. NIS controls my internet software filewall security, NAV controls my virus protection, SpamKiller controls trash sent to my email boxes on the server side before they ever hit my system and so on....

Hmm, why do you need the Virus protection if you have NAV which is the best? I've found that running multiple virus protection relly screws up your system. Also, why would one need a IT Wizard to delete orphan registry entries or misplaced files? All one needs is a system scan for the file to make sure it doesn't exist.