A710- differences between modes

One of the subjects puzzling me when using any digital camera is the choice of the shooting mode. It's not that I don't understand the implementation of each of them. I just doubt which one would suit the best. I know, that expierenced users advise to use PASM modes, but I don't like to drop the advantages of Auto/Scene modes as I described in my recent thread:

http://forums.dpreview.com/forums/read.asp?forum=1010&message=22047071&q=a710&qf=m

Recently I used the Portrait mode a lot in a party. Examining the images I discovered, that those shot in this mode where slightly blurry, soft. So I decided to do a test.

I took indoor images with flash of my son in Portrait and Program modes. Not suprisingly they differed quite a lot. The image in Program mode was as I would call a normal standart. But the image in Portrait mode was different:
1. notably less saturation or either reds on skin tone

2. notably less details that looks like stronger noise reduction, but I quess it's more likely to be reduced the Sharpness parameter in "My Colours".

I am allmost secure for these adjustments being made in Portrait algorithm under "My Colours" settings. So I will never use Portrait mode in parties any more. But what about all the other Scene modes? We never know what settings can be applied in them! That's why I wish the algorithms would be described in depth in manuals.