You want to determine your load-balance method based on an analysis of your traffic patterns. If a single host will be receiving most of the traffic on an etherchannel, it's destination IP will remain constant. In this case setting your load-balancing algorithm to use source IP's which will likely differ would help distribute the traffic more evenly across the link members.
If you're using PAgP, auto mode will only negotiate an etherchannel if the far-end asks for participation (desirable mode). LACP passive mode works the same way.
