I pick what I want based on its primary use. The fact that you can use a lightbox variant to show a dialog box, doesn't make it a good candidate in my mind.
Generally if I need to show photos or another iframed web page, I use a lightbox variant. Two that we have used at our studio and been happy with are:
- Slimbox 2 (Just photos)
- Colorbox (Pretty much any type of content)
For dialog type behavior, I highly recommend using jQuery UI's dialog. It is in active development, and is super customizable.
[rant] Whatever you do please don't use SimpleModal unless you need its special type of callbacks. Otherwise, when you try to hook into an onClose
callback, you'll find yourself having to perform the actual closing of the box. Just my two cents on that one. :) I just know it has come up a few times here in SO, and it just feels awkward to use IMO [/rant]