Hi Abhi,
Password protection is vulnerable to phishing attacks, there are chances that anyone can hack into your data or see what you are transmitting to your third party.
Certificates on the other enable use of asymmetric key exchange method between 2 communication parties using the private key and certificate pair. Your data will be nothing more than a jumbled bit of information for anyone who tries to hack through 
Hope this explains!
Regards,
Karthik