The best pressure washer under 100 Pounds is the one that can do its job with the least amount of effort as possible. If you buy a machine that has no power source and you have to pull it by hand, you will be spending more time on the task than necessary. The best models have electric pumps that run off of batteries or you will find that they come with rechargeable nickel-cadmium or lithium ion batteries that allow for recharging when the power is turned off. This allows for the power source to stay on even when it is not in use and that means it will get good use from day to day. They also come with longer cords to keep the cord from tangling up in between uses.
The best pressure washer under 100 watts is one that does what it says it will do without resorting to battery recharging or having to remember to charge the washer between uses. They also have features on them that make it easy to clean up your machine. For example, some come with a detachable tray to catch all of the crumbs and debris and this makes cleaning out the washer much easier. You also want an edger that has a smooth motion, so that you do not scratch the surface underneath.
While price is often seen as a factor in finding the best pressure washers, make sure that it is not the only thing you are looking for. Make sure the quality is worth the price and that it will last you for the length of time that you need it to. In other words, buy the best pressure washer under 100 watts that you can afford to run.