What's the best way to build a application...
Electron or JavaFX ?

Let's the debates begin !!!

Depends on what language you already know.

I'd probably say JavaFX, as you have more control over your window(s), and at least some access to native features if you use Java. Electron on the other hand is known for having extreme resource usage, and is generally not that beloved of the users.

React-VR, duh

Well there is not really something to debate. It comes down to the recuirments you have for the project and the experience your team has.
You nedd to pick what suits you the best. For exmaple if you have a web application thats already running in production and you only want some of the native functionalitys of the OS you would go with electron, since is faster to develop and you dont need to change the code that much.
On the other side Java is a completly different enviorment and language. You would go this way for something like buinsness heavy application.

Worked once with javafx and it was pretty chill. No struggles or issues and looked great

@systemctl the last 3 months ish electron has gotten a lot lighter, I have no clue how they did this but my application only use about 70-90mb ram (all processes counted)

I use electron because I know JS a lot better than Java. It really depends on what you're most comfortable in as both are viable on 2018. Play around with both and see what you like I guess.

@Stocken Oh DAMM, doesn't know this :O

Assembly. Make the Gui by drawing individual pixels on the screen.