Which is a better software to have as an addition to photoshop?

Cats vs. Oranges.

Lightroom is a great app for Raw shooters, especially high-volume shooters. It makes non-destructive global edits.

ImageReady was a web-prep app for photographs. It was never available separately, and as of Photoshop CS3 has been discontinued.

If you want a Pro raw converter, then you should take a look at Phase One´s Capture One http://www.phaseone.com

It is not as nice at first hand as lightroom, but is the best converter on the market.. and for me the result is way more important than the look of the program.

Jasz