The most critical factor in cloning an operating system onto many different machines is how quickly it can be done.
Speed is of the essence.
The methods listed above suit different environments. For instance, if you are happy to take the lids off your machines and only have a small number, with very complicated configurations, to do then the direct disk to disk method may be best. I tend to get a few machines at a time arriving for setup, and I borrow an old one from somewhere and use the crossover cable method to clone to the new machines.