The Holy Grail of evaluation is to arrive at a position where you can accurately compare like with like. Even very experienced procurement teams can find this difficult, frequently having to ask supplementary questions, conduct further interviews and so forth before they arrive at a verdict. Having a scoring system that you can apply equally to all suppliers who bid or quote helps.
The important thing to keep in mind with evaluation is that all decision makers need to agree with the method used. It is pointless going through an evaluation exercise, using up your valuable time, and then having someone else decide ...