Well, there is one thing I didn´t understand in what you posted: are the two categories in the competiton in Singapore, or are you talking about the difference between pro. competitors and amateurs?
If the answer is the first one, well, I think that you always have to get to amateur competition. Why? Well, if you are a beginner, or middle magician, who´s not dedicated profesionally in the magic world, you have more possibilities in an amateur contest. But if you are a professional magician who enters the amateur contest... then you'll win for sure!
If you are talking about the second, I think that in a contest, an amateur with good work could do better than a pro even.
All the best magic,
Pablo Tejero
"The Magic is in the air, you just have to... breathe it!"