to compare you need to look at :
Water Flow Rate in Litres Per Hour 360
Maximum Bar Pressure 120
obviously the higher both of those are, the better the pressure washer. Generally speaking the higher the first number in the model name, the more powerfull and higher up the range it is.
The problem comes with the fact they introduce new models as often as clothes catalogues do clothes - like every 6 months or something stupid. This can lead to retailers discounting older models, making higher performing models with high model numbers, cheaper than models with lower numbers and lower power because its last years model.
However pressure washers dont really have "this seasons style" so nobody can tell whats the new model and whats the old.
Just try and get as high a model as you can, for as cheap as you can, and use the above stats to compare with other models.
i'd have to agree with Wicksta about the patio cleaner, it's pretty useless, even for decking, if anything, it leaves streaks where t's cleaned and missed bits. I found the vario lance to be best for cleaning decking / concrete paving etc.
seconded. Its utterly useless. It never gets all the grim off, and you end up having to go back over it with the normal hose anyway. If you'd started with the normal lance to start off with, it would be a lot quicker.