While both can result in quality books these days, it's still rather necessary to go through a traditional publisher if you want your book to end up on bookstore shelves to be sold. Don't fall for the trap of "vanity publishers" who often promise to get your book into bookstores, yet require YOU to pay them. Any real publisher will pay ALL costs involved in bringing a book to market, as well as pay you for the book. Anyone that requires you to pay is not a publisher, but at best a printer (and at worst, a scam.) If you decide to go the self-publishing route, use a good service, one that doesn't promise much more than getting your book printed (and possibly ISBN registered) for a fair cost. There are print on demand services like lulu.com which are rather good for self-publishing, as you're basically only paying basic fees to get going, and they're not promising to get you onto the shelves at barnes/nobel or anything.
Bottom line is just be cautious and make sure you read up and research whatever company you go with, as well as what rights you're actually selling. There are a LOT of scams and shady companies out there.
