I am not into jewelery. I would not choose either of them. I prefer Opals. They are my birthstone and I think they are prettier. I don't even wear a watch.
I think Pearls are more elegant than diamonds.
For a specific event? Pearls are more conservative; diamonds are flashy, so if it's for an event, decide the look you want. If it's just to have, diamonds can be worn almost any time, but pearls are usually reserved for special occasions.