There is a big difference in the rakes and in a furminator.

Furminators penetrate past the top coat/guard hairs to the undercoat, which rakes do not do. A rake skims the surface and is more abrasive, the furminator is just a flat edge as far as the dog is concerned whereas a rake has teeth. Run them over your leg and see how it feels.

Furminators also work much faster. I used the large on my horses and let me tell you they work GREAT and much better than any grooming rake. I always use a rubber curry, or like what I forgot to add the other day a Kong Zoom Groom:http://search.ebay.com/kong-zoom-gro...fsooZ1QQfsopZ1
First, to loosen top coat, release oils from the skin and work at any soiled areas or dirt. Then I use the furminator to brush it all away.

You can get Furminators and Zoom Groom on Ebay for great prices, a lot less than your average pet store.