Which is better index.html or landingpage.html for ppc adwords landing page

We have a car site the run with google adwords. Before we use to land it on our index page but now after a suggestion from consultant we created a landing page where we point our ppc.
The new landing page has sign up which bother me. You know some people do not just want to give their contacts.
If it is in the index page then, it is visitors discretion whether to proceed with the registration or leave the site.
What do you think guys.

See original post by AutoTerminal