Hi! I need help with the next problem:

I have two domain names (www.myexample.com & wwww.my-example.com..) points to the same Web site. There is no any diffirence (one site is mirror of other one). But Google defines em as different (each domain has its own ranking and appears in SERPs on its own position) The only difference in pages cashed by Google is rotating banner. Why Google doesn't understand that one site is mirror to other. May be because of banner?

If I make 301 redirect, will google transfer pagerank, everyone say that it will, but I really afraid of loosing links. Will Google transfer links?
And how google will define which of them to ban?


All answers are greatly appreciated...