Which is fast as1.0 or 2.0 or 3.0

hi guys

i wanna know a simple question.i hv flash8 installed on my system and i wanna know in which version of AS i should code…i know AS 2.0 is compiled down to AS1.0 bt is their performance enhancement if we code with 1.0. With Flash9 beta released then agian the question is same??