I am not an expert on Flex, so I cannot personally give you a valid comparison. However, from comments I have heard from Java developers, they like the flexibility that JavaFX gives by allowing them access to the full capability of the Java platform. They are not limited in how they solve their problems.
In my opinion sir, I must say Flex is very cool, very mature , but for somebody of Java background JavaFX is the way to go, I am saying this due to my personal experience, I learned JavaFX and because of all this RIA war thing decided to take a look in Flex platform and it was really impressing(I even finished a book in 3 days) during this time Oracle bought Sun(I started flex on 18th April) and whole JavaFX will die become the buzzword for few days, but I was addicted to the way JavaFX seamlessly allow me to use Java classes and libraries and because same app in JavaFX can run on Browser and Desktop , it was effortless(flex do this with AIR platform but code re-write is required) the only thing I miss is Flex's way of communication to PHP/ASP/whatever, this is not available in JavaFX but it is on roadmap of jfxtras so we'll have that soon.
Jim Clarke wrote:JavaFX gives by allowing them access to the full capability of the Java platform.
Yes that's true, but talking about Flex, it is possible to have native access to java methods through a platform "BlaseDS" which it's open source too, and this combination it's pretty powefull because Flex it's very cool and allows you to develop cool visual interfaces for presentation tier and you have the power of Java for business process.
SCJP 5, SCWCD 5
Joined: Oct 11, 2002
Flex has a handy HTTPService that is good at reading data from a URL. Where I work we write the services in Java, then consume them via HTTPService in Flex.