The simple answer is that superior insurance offers you greater cover than the standard.
We highly advise you read the policy documentation before deciding which policy is right for you.
If you refer to the Statement of Insurance for each policy there is a table summarising the benefits, what the inclusion for each policy is, the excess for each section of cover and the maximum amount you could claim back.
There are many inclusions and exclusions within both policies so do make sure you read everything so you know what you would be covered for.
All our policy documentation can be found here.