You will find here almost all you need to understand witch way is better:
http://www.plextor.be/English/pdf/The Process of Writing.pdf
As a conclusion, "High-Speed recording is not always compatible with High-Quality recording. The goal is to find the best compromise between quality and speed". But this is regarding Plextor; for the average CD Writers I think the Quality suffers greatly at higher speeds and you will see way after reading the above document and maybe others.
About speed, I don't see how the stability increases with it. First of all, it sounds wrong. I personally use 8x as the compromise between quality and speed.
