HA fillers, in the United Stated sold as Restylane, Perlane and Juvederm have completely replaced Collagen. Allergan, which sells Juvederm and sold Collagen, has stopped production of Collagen. With the introduction of HA fillers, the demand for Collagen evaporated.
HA filler are softer, more compliant and last longer. It's ease of use is about the same as Collagen. Collagen was better for stubborn fine lines at the margins of the lips, but it lasted only 3 months (or less) time. HA's last twice as long, and are better for kissing. Not only do my patients tell me this, but their partners have too.
I have a series of articles on my blog regarding lip enhancement, including fillers and the alterantives. I link to the HA filler page is supplied below.