Advantages:
The hit rate can be quite high due to there being so many records available.
The service is quick, and usually supported.
Use of the internet.
The protocols used can be suited to the local system such as SCIS in Australia with particular Subject Headings.
Disadvantages
The cost is an annual fee and can be quite high.
The rate at which items are catalogued can sometimes be delayed due to the volume.
Schools may not need the volume of records to search through and may not get cost effectiveness.
Reliance on the internet