Having a shared IP between a dedicated IP, is like the difference between living in an apartment or living in a single family house. although its true you can live in both, with an apartment you have to share the building with many people, and if there is ever a problem (plumbing, electricity etc ) you might get effected, If you have your own house its a more comfortable experience, you have full control of everything that happens plus a lot more space.
As mentioned above having a shared IP is one of the reasons why many people have gotten banned from the search engines. We know how important your website is to you and getting punished for what someone else does is not what anyone wants, or having to pay up to $30 for a dedicated IP. That's why with IX web hosting when you sign up for a shared hosting account you'll get up to 15 Free dedicated IP addresses.