Landlords house insurance is a little different and has a couple of extra responsibilities. You can also get some cover for loss of rent on your investment property.
With a landlords extension on most house insurance, you maybe able to protect against loss of rent and malicious damage(usually capped). Losing rent from flooding and fire can be protected against.
With a rental property insurance there is generally additional requirements for the landlord. Basics like having a rental agreement and lodging the bond is of course important. However you may also find that the frequency property inspections are a factor with your current cover.