The best way to tell the difference between a cheap mower and a quality machine is to use it for an hour! If you still feel fresh and relaxed afterwards, chances are you are using a John Deere.
Blade Brake Clutch
The moment you release the grip, the Blade Brake Clutch (BBC) stops the blades but leaves the engine running. This lets you empty the collector and get straight back to mowing, without having to restart each time.