You might find that - depending on your previous experience the Simplicity might be the better option to start with, or a McCalls pattern which is not 'costume' but more suited for a modern wedding, possibly.

The Simplicity patterns are just that - simpler, less tailored, and they can look a bit amateurish if sufficient care is not taken, but you can get bogged down in a McCalls pattern which might have too many features - umpteen buttonholes for instance, which make the project too daunting, or too easily done wrong.

Different patterns will produce garments which have very different looks, and you need to consider just what effect you want to achieve. However - the material chosen will have quite a significant effect on the outcome. You do need to match the fabric and the pattern. Usually there will be suggested fabrics listed on the pattern envelope.