The major difference is the User Interface which is completely different between the two versions. IPLocation Mini only shows your IP address and country, while IPLocation shows you Timezone, ISP name, region and city.
Even more important though is the full featured map, included in IPLocation, showing the geolocation of your IP address. The map is fully zoomable and completely interactive.
Note: At the moment Data about Region and City is only available for certain locations, for this reason also the map may not be accurate. This may change in the future as more location are added.