Hulu Plus has more current TV shows, where episodes are only a day behind their broadcast TV counterparts. Netflix, on the other hand, has a far better, and wider, selection of movies and TV shows, with full seasons.
Netflix also works on a larger number of handheld devices, and TV appliances. I own a Roku box, and use it to watch Netflix. I have ordered Hulu Plus in the past, but only a small percentage of shows were available to me, and a lot of the shows that were available were the same types of shows I could get on Crackle (which I also get on my Roku box) for free.
Netflix is $8 a month for unlimited streaming, and the vast majority of their content is in HD. Hulu Plus is also $8 a month, and they have commercials during their TV shows (Netflix has no commercials). It is my opinion that for most people, myself included, Netflix is far superior to Hulu Plus, and that Hulu Plus is only worth getting if you don't mind watching TV shows on your PC, and that you're okay with commercials during those shows, and still paying $8 a month for that option.
In short, Hulu Plus has very limited appeal.