Oddly enough I think that Cleanup is the vicious one.....at least it always manages to find things to remove that Ccleaner has left behind.I think it's a bit like Adaware Vs Spybot S&D....best bet is to have both but should you only want one, then my prefence is Ccleaner if only because it is frequently updated and includes a more than half decent registry cleaner.
Disk Cleaner(Free)from click here never seems to get much of a mention. Its a good cleaner which opens quickly and tells you immediately how much clutter you have on your pc without scanning first.You can add plugins if you want.
Also, Advanced Disk Cleaner (Free) from click here is good for cleaning the temporary files (non internet) which CCleaner and Disk Cleaner don't bother with. Very quick scan.
CCleaner is probably the best of the lot but it still doesn't clean the Opera Cache on my pc so I've added it as a custom folder.
There is so much choice, you could spend your life downloading good freeware cleaning programmes