If you've managed to cut your choice of dishwasher down to a small selection, you will probably want to compare dishwashers. This is obviously beneficial, as it helps you work out which dishwasher offers the best value. When you compare dishwashers you will normally find that dishwasher dimensions are the same or very similar, but the features can vary wildly. 

Things to look out for when comparing dishwashers:

1. Price

2. Noise Levels

3. Energy Efficiency - What rating is it?  A rated dishwashers are better for the environment and will cost less in bills, G rated are clearly not so good.

4. Quality of the wash - How clean will your dishes be? Will dishes need pre-washing?

5. Speed of the wash

6. Other features - Will you actually use these features?  Are they just gimmicks you are paying extra for?