It's not much of a guide as much of a pic showing different shadow qualities on the same angle:

Fast looks best

Fast looks abit to dark imo, so i think "high quality" looks the best if you have a decent pc

I can't see much difference o.O ive always made sure that I use High-Quality. Makes a big differnce
from the un-computed shadows of the map.

Tuta says:
Fast looks best

agree
although because I will never use high quality because on my laptop it takes at least two hours

Hitchy says:
Fast looks abit to dark imo, so i think "high quality" looks the best if you have a decent pc

It's a cave, they're dark

i prefer very fast for online playing.

Could you please add a comparison screenshot for Ultra quality lightmapping, Dominik? In my experience, it is much better than High quality in complex scenes, such as ones which have lots of colors intermixing and/or have gaps in the track which allow light through, but if the environment is bright enough (typically only happens with a mod environment), this setting will crash the game. Also, note that it requires a powerful GPU if you want to avoid 30 minutes or more of lightmapping time (my GeForce GTX 460SE allows me to perform most Ultra quality lightmapping in 15 minutes or less).

In case you don't know how to enable Ultra quality lightmapping - since it must first be enabled to show up in the list of lightmapping options - here's a short little tutorial:

1. Start up ManiaPlanet using the shortcut on your desktop.
2. Click on the "Configure" button from the window which appears.
3. Click on the "Advanced" button on the lower-right side of the window which appears.
4. Click on the "Compatibility" button from the window which appears.


5. Make sure the check-box next to the words "Lightmap quality ultra" is checked; otherwise, click on the check-box to do so.


6. Close all the configuration windows you opened by clicking the following buttons in the order specified:
a. "OK" from the "Compatibility" window.
b. "OK" from the "Advanced" window.
c. "Save" from the "Configure" window.
7. Create or edit a track in Trackmania2.
8. Create the lightmap for the track.
9. You will now see "Ultra Quality" from the list of lightmapping options.

My question here is: Does it make any difference in performance when you drive the track?

So far I used high quality shadows in my maps because I had the feeling that you could see better in darker places.
As far as I can remember I wasn't even able to use the 'very fast' option when I validated the maps - only while I was still working in the editor.

I think it does. I sometimes tested my maps with fast computed shadows and the dark parts were really dark and when you came out of the darkness, you got totally blinded by the light, unable to see a thing, so in my opinion it definitely has an influence on how good you are able to drive a track. High quality shadows make the transition from dark to bright parts much smoother (at least it seems so to me).