When I'm not in school, I sell cameras, including the ones listed in the above posts. First, if given the option of glass or plastic lenses, go with glass. They will be slightly more expensive, however, they hold a finer mold than plastic will and as such, overall image quality is much better. The ones you are looking at use glass.
Between the two, for model photography, I would lean towards the Canon for a couple reasons. First, the ability to easily add on macro rings is very nice (Kodaks can do this as well, however, in my experience, the adapter is more difficult to find). A three ring set that has a +1, +2, and +4 ring for a combined +7 capability is available for under $50. I have this setup for my camera (Canon PowerShot G3) and I can get amazing closeups. If I add a lens for taking pics of models, I generally only use the +2 or +4 ring as I find they are more than enough (this pic was taken using the +2 ring - http://gallery37976.fotopic.net/photo.php?id=2367897
). For other detail work, you may want to combine them...sorry, got a little sidetracked there. Should you decide to do this, you will want control over your apeture (the Av setting on the top of the selection switch). A lower setting (ie. the 2.4-2.8 most auto settings lean towards) will result in the picture having a very small area in focus, the rest fuzzy. If you force it to a higher setting (IIRC, 5.6 is the highest on the A70), more of the pic will be in focus.
Another option mentioned above was the Nikon line. Generally speaking, OOtB Nikons do have an excellent macro mode, however, the addition of lenses is limited to only a handful of their models. At the same level you seem to be looking at in a Nikon, you would be looking at the 3100, which has an excellent macro mode, but will not allow you to add lenses on. The 4500, while an outstanding camera, is going to be about twice as an A70, 6340, or 3100.
Hope this helps you a bit. If not, feel free to post here or fire an e-mail my way.