When developing an intranet application where the target browser is IE only (IE6 - horrible I know) is there any reason that we shouldn’t use the showModalDialog() feature of IE to display dialog windows?
My colleague prefers using showModalDialog() but I prefer using a jQuery plug-in such as FancyBox, FaceBox or ThickBox instead.
It really depends on what you are doing, but the plugins you listed are not really the equivalent of a dialog window. They are more for a nice/fancy display of photos and content.
I would recommend with going with something non proprietary because your company can't stay on IE6 forever (Though it seems like it some times!).
I would also recommend looking into the jQuery UI library and using their Dialog widget to provide a rich user experience.
I would avoid showModalDialog just because at some stage in the future IE6 will be depreciated and you will have to go back and fix it all. I know some large organisations are slow, but do you think they will still be using IE6 in 2 or 3 years?
On the other hand, if it is a consulting gig, do it this way and then in 3 years time charge them again to fix it.