Multisite with search functionality I was facing an decision about a project. We have a website in drupal 7 that talks about cars. Now we want to talk about motorcycle. The basic layout will be different, i mean the header and footer. 

We want to be able for example a user in motorcycle if search for a car can show (if exist) the result  from the cars sites and the link will get him to the main site.

Can we achieve this kind of behavior ?

How i want to look
So we have Option A : moto.mysite.com
Option B will be mysite.com/moto/
I would not use a multisite for this.  Instead, I would do Option B (mysite.com/moto).

Then I would use the Themekey module to set up different themes.  If you want the two parts of the site to basically look the same, you can make the motorcycle part a subtheme of the theme you are using for the car part.

If you do this, then you don't have to worry about integrating the data; you will have two parts of the website that look different, but on the backend all the data will be kept together.