I mean, it won’t really matter unless you really need the disc space. The full game will be listed as a separate game in your Library on Steam and if Steam handles it the same way they’ve handled other beta/demos in the past, they’ll eventually just delete the beta completely when the full game is released, so it’ll just sit in your library until you uninstall it.
My buddy was hooked on the beta weekends and says there’s more coming before the full game is released. If you want to keep playing it when they open it up for testing again, I’d say keep it installed and uninstall it before the preload happens (assuming BF6 allows you to preload it before launch).