Just found a really  good comparison chart that shows that differences between Cisco's Site to Site VPN technologies and when one can use them. Here is the source but just incase Cisco changes the archives (as usual) I will upload it to my Blog for future references: http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6586/ps6635/ps7180/prod_brochure0900aecd80582078.pdf