I used the extension tubes; they'll usually give you a better quality image when compared to proxars, especially along the edges of the image. However, proxars are much faster. I've never done close ups of people, though I have done close ups of statues of people (which are a bit different!) and I thought my 80mm lens alone was good enough, but if I needed to get closer then a 21mm extension tube worked great for me. Personally, if you want to do a lot of close-up shots of models, I'd take Bob's advice and get another lens, partly because using a longer focal-length lens is more optimal than using a lens with tubes or proxars (though not more economically optimal!) but also most people usually wont be too comfortable with a camera right up in their face, which is what you'll get when using any extension tubes. A longer focal length lens will allow you to work further away from your subject, and I think most people will appreciate that.