The ability to use VSCode has become possible thanks to the new build system. There is even documentation on how to use VSCode: Developer Guide | openHAB
Eclipse has always been the ide of openHAB as it was tightly bound to the eclipse build system so it is best supported. But the build system has changed, with, among other things, the idea that you can use whatever ide you’re best familiar with. It looks like more developers are starting to use VSCode with openHAB so experience and specific support is increasing.
To summarize. If you’re not familiar with either ide. Eclipse is probably the way to go. But if you’re familiar with java development with VSCode or you’re not afraid to try something new you should certainly give VSCode a try.