No article link, but quite simply Point to point VPN's that will continuesly be operational (site to site) then you should use an IPsec VPN. If you are using it for users and for disaster recovery, then by all means go with an SSL VPN. An SSL vpn is fantastic for users just becuase they just need a browser to connect to the network an little to zero client configuration on their end.
Firewall to firewall vpn should also use IPsec just because of the stability and encapsulation / encryption of the link. SSL is still a bit difficult to justify site to site because of the reliability of data encapsulation from the end user. IPsec can encorporate IDS/IPS. Some may argue that SSL is the state of the art, however, IPsec tunnels do not get breached (unless its internal) and are constantly upgrading stronger ciphers. SSL does this too, however the overhead (processing power and cost) may be too much to justify.
HTH
