We went with the Bluebird Bed Edger 2 years ago. It has a solid Honda 5.5 hp engine, and good ergonomics, but we have had a ton of maintenance with the blade working loose. You're looking at 1 hour of maintenance for every 4-8 hours of operation (depending on how skilled the operator is at working around rocks). You have to pull off 2 shields and reset the blade on the shaft, as well as tighten up 6 set-screws to get back in business. A real pita.
Next time I would go with the Brown.
Bear in mind that these machines are both dangerous to operators, and anything else that gets in the way. Safety glasses, ear-protection and good training are a must. Hidden obstacles like irrigation lines and low-voltage lighting cables get eaten alive, and make sure Digger's Hotline has been called before you fire her up, or it could get ugly fast.
Here are two old threads on the same topic:
Best Bed Edger Vote
Mechanical Bed Edger