SSO from Browser to SAP Web AS / SAP Enterprise Portal with SPNego/NTLM

Hi

we have NW04 Sp18 portal with ADS LDAP for user authentication ,we want use SSO for Portal logon with NT logon credentails without logon screen.

We come to knew that there two methods to implement sso

1.NTLM

2.SPnego

We have following questions

1.Out of two methods which is the best one in case

a)performance

b)implementation process?

2.what are the merits and demerits of each one?

3.which method should be used?

Please clarify .

thanks

Gopal