For somebody new to actionscripting is it better to learn AS2 first?
I`ve heard AS3 syntax is much more complicated.

In any case, AS3 will only run on Flash 9 players, and only about half the world seems to have that installed. So quite frankly I think it might be wiser for accessibility reasons to stick with the older version. Opinions?

It's not much more complicated, it's simply different. It depends what you want to do. If you make sites then it depends on the audience. You can compare them for yourself at my site if you want.