SSH is more secure than telnet. Telnet which transfer the date through port 23 flows the password in unencrypted form which is not secure. SSH is a secure shell which works on port 22 and does encrypted data transfer.
For security reasons, the new upcoming Linux distributions doesn't enable the SSH login for root by default.
To enable the SSH login for root, follow the workaround:
1. Open the file /etc/sshd/sshd_config with your favourite editor. Search for the line PermitRootLogin and uncomment it:
Save the file through :wq
2. Restart the ssh service through:
service sshd restart
3. Try to SSH for root user through putty and it should work.