When comparing JavaFX vs Tk, the Slant community recommends Tk for most people. In the question“What are the best cross-platform GUI toolkits?” Tk is ranked 9th while JavaFX is ranked 18th. The most important reason people chose Tk is:
Once you understand how to style, the styling can look great.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro FX uses hardware acceleration and Java is fast, so good for 2D action games
Also has many built-in effects, like scale, rotate, color shifting, etc. The look and feel is simple to change later, as it uses Cascaded Style Sheets.
Pro Easy styling
Once you understand how to style, the styling can look great.
Pro Great for beginners
Easy to pick up and run with it.
Pro Easy and good looking in Mac, Linux and Windows
Pro Bindings for several languages
Bindings for Python, C, C++, Ruby, Perl, Go, Java, Haskell and more, see Languages with a Tk binding.
Cons
Con Does not automatically give you a pure platform look and feel
Cannot be used with non-JVM languages.
Con Base looks are garbage without a good amount of styling
Going with the base look for your app is a bad idea because it looks like garbage with the defaults.
Con C# support lacking
Although the Eagle Project exists, which offers Mono and .NET Core support, C# support is not standard.