I have both right now that I'm paying for and they're kind of for different things.
Hulu Plus is really great for TV, the backlog of full seasons is pretty decent but missing some big names such as House and Bones and such. I figure as they pass this "beta" phase those will fill in. The picture quality is pretty good, really fine for the iPhone and probably even iPhone 4. The commercials suck a little but are really only on first run releases, if you get something from season 1 and the current season is season 4, there won't be any commercials or maybe at most one. (Talking from experience with 30 Rock)
NetFlix is awesome for movies, although I still have looked for a decent number that I found were only offered via DVD, it's really upsetting that you can't stream them but you can wait a day or two for the DVD. Either way, right now it's nice to have the option to do both (though I hear a streaming only cheaper plan may be in the works). The quality is a little bit better but the audio levels seem to be a little lower which makes listening without headphones a little hard. The TV shows seem to be hit or miss. They have stuff that Hulu doesn't (Nip/Tuck, etc) but they often don't have up to the current season, and if they do, you've got to wait till the season DVD release sometime in the fall rather then using the summer slow TV time to catch up on the spring episodes you missed.
Probably with both you'll be able to ditch cable, or at least damn near ditch it and for what, $18 a month or something? It's honestly not that bad, especially when you can rent as many DVDs as you want too if you return them fast (one out at a time).
I believe both have been updated for the new AirShare output to TV... I at least remember for sure one was updated, I think NetFlix but I'm almost positive that Hulu was updated too.