@Ricko I have used both, recently converting two projects from STM32CubeIDE to VS Code with the STM32 extension. I am also a long-time Eclipse (well over a decade) and VS Code (5+ years) user for application development.
STM32CubeIDE is a more mature tool and has a more integrated feel for STM32 development. VSCode is a better code editor than Eclipse and has better C/C++ support. But the STM32 extension still has some rough edges and is not well documented.
I spend a lot of time learning how do do things in the STM32 extension. The extension feels incomplete. For example, in Eclipse one can just click on an IOC file and it is opened in STM32CubeMX. Not so in VS Code. The IOC file is opened in a text editor. One has to start STM32CubeMX, then open the IOC file from within STM32CubeMX. I have had the debugger hang more frequently in VS Code. The workflow seems a bit clunky to me. Some changes seem to require that I re-open the project in VS Code for VS Code or ST's extension to pick up on them.
The CMake build system used by the STM32 VS Code extension makes build automation much easier. This is a key draw for me. The debugging experience is generally better in VS Code. The debugger view is better laid out and presents more information.
I am willing to put up with the rough edges to use VS Code. I would not recommend the STM32 VS Code extension for training or for new developers. STM32CubeIDE is a better choice here. The workflow from creating the project to programming and debugging on a dev board takes fewer steps and has a more integrated feel. But for seasoned developers with a lot of VS Code experience, I recommend using VS Code with the STM32 extension.