Hi,
Ok.....On analysing I conclude that I will go with multisite SSO , which will help me to connect all 3 vCenter in a link mode as well as for future perspective if SRM comes in my environment then SSO with multisite is mandatory. Hence going for multi site SSO.
Just one more question I would like to clear , Should I install a seperate server for SSO ? OR Should I install with the vCenter server ?