Previous experience of debating and mooting seems to be a very common concern. Having been involved in debating in both High School and university, I can firmly say that it is of very little advantage.
This is for three reasons. First, mooting is unlike debating. The style required and the depth of research / knowledge is different. This is not to say that debating requires no knowledge, indeed it is far from that. The critical difference is that mooting requires specific knowledge on a very narrow area, meaning that you are expected to present a smooth but readily understandable submission on a complex area of law.
Secondly, the style of speaking required is different. Indeed, I found that my debating experience was of significant detriment - one is often tempted to use rhetoric and other verbal techniques - generally not accepted in mooting.
Lastly, everyone is new to mooting in the beginners competition. Therefore, no-one has a fundamental advantage over anyone else. It is true that debaters may be more confident in standing up and delivering submissions, but it does not mean that they will win.
