money......it will always come down to a question of money...LOL
there is no one grinder that everyone can say is the best for the money...each grinder is different, some are better than others,,,some are crap,,,some are over priced but still good.
Some are worth every penny no matter how much they were up-front.
Im not too sure about getting a used grinder,,,you never know what life is left in the motor,,,but if you do get a used one and the motor dies, you can just get a new one and stick it in.
many grinders sold today dont come with a motor, be carefull when you do get such a one that you understand you need to now get a motor..