I have a question. Does the Multi-Domains plugin need

Hi,

I have a question. Does the Multi-Domains plugin need to run alongside the Domain Mapper plugin? If I have them both and map a domain to a website, I can view the website while being logged in. If I remove Multi-Domains and keep only Domain Mapping I get logged out when trying to view the website on the front end.
I use Pagelines to edit my themes so I need to be able to be logged in on the front end to make any changes on the website.

Also, when I remove the Multi-Domains plugin my sites load a lot faster. Why is that?

Thanks,

-J