Is good idea to use gerrit to host the git repository instead of gitolite or gitosis?

If you're going to use gerrit at all, you might as well use it for hosting as well as code review -- the workflow is easier that way, as gerrit will manage merging your reviewed code into its repository, and that's what you want to be publishing -- if you host elsewhere, you're going to have to either set up a method for automatically pulling from gerrit or you're going to have a way for your developers to bypass the code review by pushing their changes straight to the hosted repositories and ignoring gerrit altogether.

Recent versions of gerrit can integrate gitweb, giving you the nice web interface to browse with, but protected by the ACLs you've set up.

I use only gitolite for the fine-grained ACL it provides.

For the code-review part, I use FishEye (not free even though free licenses exist for certain projects) and Crucible (both from Atlassian).

That allows me to separate the two features (ACL vs. Code review) on two separate servers.

You can use gerrit if you need code review, it has its own ssh server that integrate git.

Gerrit use user groups and allow you to specify permissions at desire level, it also have some features to accept contribution from external developers easily, you can force developers to accept some TOS.