This paper focuses on the experiences gained from defining design metrics for SDL and comparing three prediction models for identifying the most fault-prone entities using the defined metrics. Three sets of design complexity metrics for SDL are defined according to two design phases and SDL entity types. Two neural net based prediction models and a model using the hybrid metrics are implemented and compared by a simulation. Though the backpropagation model shows the best prediction results, the selection method in hybrid complexity order is expected to have similar performance with some supports. Also two hybrid metric forms(weighted sum and weighted multiplication) are compared and it is shown that two metric forms can be used interchangeably for ordinal purpose.