On premise, off premise, internally supported or outsourced is the normal conversation regarding any IT system or service and the answer is usually different for each company.
To work out what is right for your company you need to consider whether you are happy with the capital investment, how sensitive the data is, what backup strategy is required and how it will fit in with your business continuity plan, how you will handle upgrades, are the IT skills up to date and how will they keep refreshing them?
In most cases if IT is not your primary business then it is likely to become a distraction.
Outsourcing can be the answer to many of these problems by providing technically competent staff or facilities that exceed the functionality of what can be accomplished in house for the same costs.
You need to ensure that the cost savings or benefits provided by outsourcing are not negated by the increase cost of negotiating, the transactions, monitoring quality and management.
Remember to have a succession plan and exit strategy. Beware of potential for costly changes to the service and a need for better planning due inflexibility of the offered services.