The green works unit comes with a foam cannon, that is a 30$ value right there. So if you are not planning to modify the setup, the Greenworks one is a much better value. On the other hand, if you are gonna change the hose and gun, then I would assume the Ryobi is a better quality machine. So it really depends what your goal is. If you want to get a basic unit at the great price, the Greenworks is pretty much unbeatable at the 59$ pricepoint. Otherwise, for a more professional setup, I would go with something in a higher quality bracket. Many people have said the Ryobi delivers a lot of power for such a small unit.
Sidenote, I have used my own pressure washer today to rinse off my car. Temperatures are finally a bit over freezing here in Montreal with a high of 42F today. After using the coin operated pressure washer all winter, I must say I was pretty disapointed with my pressure washer. My unit is 1700 PSI. I had trouble removing dirt on the paint. It will do it, but it takes so much longer than using a higher pressure unit. I am thinking about getting a higher pressure unit now. Only issue is portability since I am mobile. The 1700 PSI unit is heavy enough, I think that a 2500 or 3000 PSI unit would be too heavy to carry around and move in and out of my Dodge Caravan on every detail. Not sure what to do ;( And I did order a replacement hose and gun although those could be used on the new unit.