The only visual differences between 3.1 and 3.9 are:
- the background picture -> is already possible in 3.1
- the colorful icons -> can be achieved by installing NewIcons. You have to find some good-looking icons yourself, though.
- AmiDock -> can be replaced by ToolManager or similar.
Regarding speed, there is no difference between OS3.1 + NewIcons and OS3.9.
Of course, in order to have a nice wallpaper and icons with many colors, you also have to choose a screen mode with many colors. While MagicWB only needs 8 colors, NewIcons needs at least 16 or 32 colors. The backdrop picture might need even more.
Considering that more colors also cost more chipset power this means that on AGA it might get slower. However, I ran my A4000/030 on Multiscan Productivity with 256 colors and NewIcons for years and never missed anything. So you should at least try it out.
OS3.9 itself is not a single tick slower than OS3.1.
Bye,
Thomas