The reason I say that it's good to go with as3 is because of as3's similarity with java in it's reliance with listeners. Also, from my understanding, as3 was built to be more like java for the purposes of speed improvements. In the end the similarity doesn't matter too much since the syntax between all three are relatively close, the important thing is learning to learn. I think that it'll be easier to learn something like as3 considering the fact that you'll be able to stay within the same dev environment.
Just wait until you get into a syntax that is radically different, definitely was a shock for me when I started to learn monkey and also when I played around with objc.

