I have no idea as some of the judging seems to be unexplainable. The judges are different each time and unconnected with the club (although they do get paid for their services). Most have Royal Photographic Society accreditations and also have done courses for judging. The things most judges have in common, however, are looking for composition ("Rule of Thirds" in particular), subject matter, sharpness, and exposure. Some judges also like abstract photos whilst others detest them (the same with cars, aircraft, or wildlife) and the whole matter becomes more subjective than technical. For example, tonight's judge ignored 'blown out' images (e.g. extremely overexposed sections of sky in a sunset shot, or an overexposed swan where the details are lost on the feathers to be replaced by a bright white patch), whereas another judge would severely penalize such an image.
My solarized boat in the Sussex Regnum Competition springs to mind; it came last in my round against nine other 'normal' photos but, having said that, so did all the other artistic style photos entered in the other rounds. Interestingly, anything with a bird (feathered variety) or a landscape scored very highly.
I hope this answers your question, Susanne, but if I get the chance later this year I intend to do one of the judging courses myself so I can understand some of what is going on.