well it's not a pro or con, it's just the wrong technology, just like there are no pro's and cons to running a car off of pasta and mashed banana's, as good a fuel as they may be to humans. channel bonding helps you in the diagram here where one of the two cables busts: http://en.wikipedia.org/wiki/EtherChannel but that's not your topology is it? you're more like this: http://lartc.org/howto/lartc.rpdb.multiple-links.html so where as the first question would be "how can i use two network interfaces to increase traffic throughput and resilience to a single LAN?", your question is "how do i use two totally seperate and unknown to each other isp's to reach the internet?"

i do really think i've given you suitable advice earlier on, is there some part of it that's not making sense?