The biggest drawback with secret key cryptography is the issue of handling the distribution of the keys. The recipient needs to be in possession of the secret key before you can send the encrypted data. Making sure that the key gets distributed securely is again a risky deal. But symmetric key algorithms-due to their speed-are usually preferred over key encryption where a huge chunk of data is concerned. 
But if you want a higher level of security, public key or asymmetric key algorithms are a better deal.
Public key encryption is considered significantly more secure than symmetric key encryption, not because of the algorithms used-in fact, the algorithms used in both types are equally secure but because the method of key transmission is so much more secure.
Going back to our earlier example where you need to send your tender document to your boss, this is what you would do using the public key algorithm: your boss would generate a set of keys - public key and private key. He would then send you the public key, which you would use to encrypt the document, and you would transmit only this encrypted document back. And he would use the other key of the pair (private key) to decrypt the data. So, unlike symmetric key encryption, here the private key (actual key used to unlock the data) is never transmitted. So even if you publish your public key on the front page of the Times of India, as long as your private key is with you, your data is safe.
