Red Line oils are made with lots of esters and hugely robust additive packs. In a nutshell, and as I understand it, that means:
1. You can beat the [censored] out of your engine and the oil will take it like a champ.
2. It will stand up to any physical stress (RPM, torque, turbo) or any amount of heat and not even blink.
3. The oil will run extremely consistently until a certain point (usually 7k-12k miles, depending). After that, its performance will deteriorate fairly quickly.
4. Fuel dilution and water contamination (e.g. from lots of idling, stop-and-go, short trips, etc.) will drastically shorten the oil's life.
In other words, Red Line is a good choice if you like to drive very hard and/or have a highly modified engine.
Someone correct me if I'm wrong, but that's the gist of it AFAIK.