Is a passive brace or a smart vibrating trainer better?

It depends on your goal. Passive braces (like ComfyBrace and Fit Geno) physically pull your shoulders back and are cheaper, but reviewers note they only help while worn. Smart trainers like the Upright GO 2 vibrate when you slouch to build awareness, and across mainstream reviewers and specialist subreddits they tend to be favored for actually retraining habits, though they cost far more.