The originals are the legitimate Region 1 sets that are designed to be sold to a North American audience. There are two types of bootlegs of which I am aware. The first are the "fansubs," mentioned earlier. These are subtitled versions of the original Japanese versions, usually of rather poor quality. There are very few places that have the nerve to charge money for fansubs, although I suppose they are out there. You should probably avoid these, unless you like buying junk.
The second type of "bootlegs," are English dubbed versions of the originial series. They should have the same English audio tracks as the standard versions, but there are a few important differences between these and the "real" product. First, they are generally 50% or more below the retail price for the standard versions. This is good for those that don't have the money to pay for the originial product. The second difference is that these are mostly Region 0/Region Free, meaning that they will play in any dvd player from any part of the world. Third, most of these come out of Hong Kong, China, etc., meaning that there is a good chance you will be paying exorbitant shipping charges to receive the product by mail (I don't know of any store that sells them).
Although the video/audio quality of these versions is more or less on par with the standard editions, they generally come in cheaper packaging (with gatefold cases being the most common, as opposed to the hard plastic keepcases of most standard dvds). In addition, they usually have more episodes crammed onto each dvd. In other words, they have no value as collector's items.
If you want to see what these bootlegs look like, you can visit the following sites:
http://www.cookiejarvideo.com/http://animecollector.com/http://www.jinkie.com/ Also note that most of these sites sell English dubbed and Japanese only dvds side-by-side. Compare the prices, region, and numbers of discs to see the difference between the different versions; however, keep in mind that I am not familiar with any legal issues that might be involved with these bootleg versions. In case they are illegal, I will add the caveat that these links are for "educational purposes only."