A world-class pianist has less of a chance of stumbling upon a zombie-virus, so I say the other one's better.
Follow your heart and allow it to lead the way. They are both great jobs. you can be a genetic engineer and play in your free time why settle for one.
Personally I'd prefer to work in genetics, but you have those who are more artsy and others who are more math and sciency, so neither is better per se
I would go with the pianist, you can see a lot of the world while doing what you love...the safer one is the engineer though!
pianist, by far
Better? Depends what you like... Obviously if you are really into music being a world class pianist is a dream...