Salesforce Enterprise vs Partner Web Services

• Enterprise Web Services WSDL—Used by enterprise developers to build client applications for a single Salesforce organization. The enterprise WSDL is strongly typed, which means that it contains objects and fields with specific data types, such as int and string. Customers who use the enterprise WSDL document must download and re-consume it whenever their organization makes a change to its custom objects or fields or whenever they want to use a different version of the API. 
•  Partner Web Services WSDL—Used for client applications that are metadata-driven and dynamic in nature. It is particularly—but not exclusively—useful to salesforce.com partners who are building client applications for multiple organizations. As a loosely typed representation of the Salesforce data model that works with name-value pairs of field names and values instead of specific data types, it can be used to access data within any organization. This WSDL is most appropriate for developers of clients that can issue a query call to get information about an object before the client acts on the object. The partner WSDL document only needs to be downloaded and consumed once per version of the API.