[robski]

OK Nogbad it is a complex subject so lets try and keep it simple.

Basically the choice comes down to the intended distination of your images.
If your images are intended to be displayed on a Monitor or printed as photos use the sRGB. If they are intended to be professional images printed in a magazine on a 4 Colour printing press use Adobe RGB.

As Jim says it is best to stick to sRGB unless your going to sell your work to a professional agency.

Lets put these colour spaces shown in the diagram of Jim's link into context.

The larger outter loop represents the range of colours that the human vision is capable of seeing.

The Adobe RGB triangle represents the range of colours that a 4 Colour (Cyan, Magenta, Yellow and Black inks) printing press can produce.

The sRGB triangle represents the range of colours the RGB phosphurs on a Monitor can produce.

So in a nutshell commercial printing inks have a wider range of greens and blues than the phosphurs of a Monitor.

If you use sRGB instead of Adobe RGB when printing on a press you will be clipping the the range of Greens and Blues that can be used.

Because the Adobe RGB exceeds the range of Greens and Blues the monitor can display it effectively reduces the overall contrast and colour when displayed on a Monitor. Hence it can look washed out.

When it comes to converting between colour spaces. In one direction you are clipping or compressing the range of colours. In the other direction you are stretching the range of colours. So instead of seeing smooth colours you may see steps appear.

So when in doubt use sRGB.