If you have 2.com serving the content from the same directory as 1.com, with no redirect, you will probably get hit with a dupe content penalty.
If you really want to move from 1.com to 2.com, and you can get any possible link trades to move to the new one, then set up a complete mirror on 2.com, or move all of the content over and put an .htaccess on 1.com that contains:
Code:
Redirect 301 / http://www.2.com/
google will find the 301s, removing the original link from its index and spider the new pages for inclusion. All pages requested will be redirected/rewritten to their corresponding location. i.e.
http://1.com/blah.html will be redirected to
http://2.com/blah.html
You'll probably see some lag from the time you do the switch and it's possible neither will show up in google during the transition.
Making that move early is better than later... I only hope the branding/seo value of 2.com is worth the stress while you wait for google to pick things up.
