Shameless plug: I do go through these options in my book, Building
Service Provider Networks (Wiley). Even there, though, I only run
through the alternatives. You will still have to make your own
cost-benefit decisions based on business policy, budget, clue level
and cost of alternatives.
A copy of which I have sitting here at my desk. Ah, yes. Beginning at
p. 344, "Multlinking and Multihoming: The Customer Side". I suppose I
should re-read that section. 
Regarding our internal network, I wish I could skip ahead to p. 517,
"VPNs and Related Services". Unfortunately, the VPN products that are
available right now are double the cost of our frame relay network.
Oh well, perhaps someday my price will come.
Thanks,
John