Definitely use amazon. I got a furminator for $20 on there!
I know you're asking about those two specific products, but I JUST saw a commercial for this tool last night and thought I might as well throw it in. I'm going to read some reviews on it to see how well it works before I buy it. The most appealing feature is the curved bristles- they say it won't scratch or irritate the dog's skin as much as a regular comb. It also comes with a mitt to help catch any loose fur. Here's a link to their website with video if you want to check it out:
I use the furminator only for heavy shedding times, and almost always outside as it does make a mess. It's amazing for getting out the loose undercoat when they are really blowing coat though. For regular use I just have a slicker brush and a greyhound comb.
I think the medium furminator is around $30 on amazon.