2 Drupal Sites and 1 CiviCRM
There is a third option. You can use two drupal sites and a third site for civicrm. 

On your Drupal sites use CiviMRF module to connect to your CiviCRM site. 

I wrote a blog on how to do this: https://civicrm.org/blog/jaapjansma/using-civicrm-form-processor-extension-to-handle-form-submissions-from-an-external

Personally I would go for this option, because you keep your CRM seperate from your website. A website might require changes/redesign over time while a CRM needs to be stable and stay the same over time. And this way you can easily change/redesign your website without the fear of breaking anything in your crm.