How to use Rules to redirect a user based on URL argument?
Well, if you're planning on doing it solely via rules, you can create a new rule for each if in your logic and then just set them to be actions one after the other. Something like this: 

Action:
  RULE: 
    IF: &lt;condition&gt;
    REDIRECT: &lt;here&gt;
  RULE: 
    IF: &lt;condition&gt;
    REDIRECT: &lt;here&gt;
  RULE: 
    IF: &lt;condition&gt;
    REDIRECT: &lt;here&gt;


This would effectively work like an if-elseif-else statement (assuming that the redirection is using drupal_goto().

But really, this sounds like a job for a custom action that takes the parameters and includes your own custom logic. It'd probably be a lot cleaner in the long-run.