I'm developing a referral system for my website, and the way it works now is to generate an unique URL like www.example.net/public/referral/UNIQUE_URL. This page is just a normal registry page like the one found in www.example.net/public/registry, but with the text "You were referred by: NAME_LASTNAME_OF_USER". Example:

Registry page www.example.net/public/registry

name:_________

last-name:_________

email:______

password:______

Referral page www.example.net/public/referral/UNIQUE_URL

name:_________

last-name:_________

email:______

password:______

You were referred by: NAME_LASTNAME_OF_USER

How is this going to affect the SEO of the site? It will be better to use the same registry URL with a parameter? O this parameter, imagine www.example.net/public/registry/UNIQUE_URL, will also affect the SEO?