I have both (actually 2 Webers) and would highly recommend both. Blackstone is unreal (breakfast, grilled cheeses, smash burgers, stir fry, tacos, and more) but if I'm cooking a steak it's on the grill. Sometimes I don't want a smash burger either.
With that said, I have a spare Weber Spirit 3 burner in great condition that I no longer need even though I still use it regularly (since I also have a Weber Genesis). If it helps you get both let me know as I'd be happy to part with my Spirit (or even my Genesis).
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