Color Space

As a general guideline:

1. If you need smooth gradations, the ability to extensively adjust your image, and like extremely saturated colors, ProPhoto RGB in 16-bit mode is the best option.
2. If you can't afford 16-bit mode and saturated colors are a priority, use AdobeRGB in 8-bit mode.
3. sRGB is the de-facto standard for digital cameras, printer, scanners, displays, the web, etc. There are less headaches using sRGB if you don't understand how to color manage documents, and if saturation isn't a large concern, you're more likely to avoid banding in 8-bit mode with sRGB as opposed to AdobeRGB.