In my opinion swing is easier to start because there are tools like the eclipse windowbuilder which enables you to create your application in a graphical interface but javafx is more likely to be used in the future because it has some great improvements over swing like css skins etc.

In swing like anywhere else what matters is how you reason through your usage of polymorphism where it s reasonable theres nothing inherent about swing that makes it more difficult to implement than it is anywhere else;i don t know anything about windowbuilder but if it s keeping you from reasoning about your usage of polymorphism or otherwise limiting or influencing your thought about other architectural decisions then the tool is probably not as great as you think the tool is and is almost certainly not worth that cost

Jigloo swt swing gui builder - home page;the windowbuilder is quite better tool