Three, Four and Nine are my top picks out of all of them.
Banner Three is the only banner out of all of them that doesn't have a rectangular box, taking advantage of the transparency and also adding a more third-dimensional depth to the banner itself by using layers in a smart way alongside good vector choice and positioning. Overall the best banner out of the bunch.
Even though Banner Four has a realistic sunflower background instead of one that matches the MLP style of things, and even though it has an unnecessarily thick outline border, the banner itself still gets my vote due to the similarities it has compared to the previous two banners used when the competition started.
Banner Nine also gets my vote, firstly because of how simple yet well-done it is. The positioning of the text and the vector is quite refreshing since it hasn't been seen before in the past, and even though it's pretty basic, it has it's own uniqueness compared to all the other banners.