Very simple. You can sell it if you feel the coin does not have the strength to survive and grow in the future. And you can hold it if you think it has good potential to grow and have a high price in the future.
Token bounty must hold or sell? In my own perspective, you should hold and keep it in a long term but it depends upon the project that you are into. If you will hold it, there is a possibility for you to make a bigger profit than you are expecting to have. It is up to you. If you are willing to wait. Then hold it.