A veneer is an ultra-thin porcelain shell bonded only to the front of the tooth, with little or almost no reduction - ideal when the tooth is basically healthy and you want to improve shade, shape or gaps. A crown covers the whole tooth and needs more reduction; it's used for heavily damaged teeth, after root canals, or for major changes.
Following the minimally invasive philosophy (MICD), the most conservative option that works should come first: if a veneer solves the problem, a crown isn't necessary. Preserving natural enamel keeps teeth healthier and more durable over time.
The right choice depends on each tooth's condition, your bite and your aesthetic goals. An examination and Digital Smile Design (DSD) lets you preview the outcome of each option before deciding.