I would like to point out to you that there are several things different between his vector, and the picture he made it from, the first being that he didn't use any gradients, and the picture has lots. For beginners getting nice curves is hard enough, making all the gradients is extremely hard.
For your first vector it looks good, but as Dœmon said, work on keeping your lines smooth. I do like how you made it your own by not using the outlines like done in the original.