This is incorrect. The difference is that lazlo and flex are tools that build fixed binaries. They are the equivalent of a c++ compiler. This is designed to be like html. That means that you can, from a web server, create pages on the fly. You cannot modify or change code on the fly in lazlo or flex. In html, you can dynamically create a page based on information in the database or other state related info. This is a fundamentally different model (and one that most of you should be familiar with) and entirely different than flex (which most of you are not familiar with).

As far as swfmill goes, that is an entirely orthogonal concept as is haxe. swfmill is a tool for organizing assets, and haxe is a compiler. That is like comparing an apple pie to a shoe.