Q: Sealed spherical bushings versus upgraded rubber or poly, which is better?

Rubber and polyurethane still flex and can introduce compliance, which softens response and lets alignment move. Sealed spherical bearings lock that motion out for the sharpest, most consistent rear end, and the seal keeps them durable where an open spherical would collect grit. If you want maximum precision and alignment stability, spherical is the top tier. If you want quiet comfort above all, softer bushings ride more forgivingly.