The benefits include greater robustness, greater performance, greater verification, greater clarity of code, greater reuse, greater interoperability.
Why a LINQ-based approach is best for application data access:
The benefits include:
Greater performance in many cases. In particular, in cases where there are important queries used by the system which interrogate a small number of properties of a large number of types of object; this is a case where LINQ-based approaches do particularly well.
Greater verification: Certain errors otherwise only detectable during testing become detectable early in the development stage.
This is a big one for your bottom line and cost of application maintenance - Greater clarity of code. A LINQ based data access architecture allows for easier and more reliable maintenance and extension.
Greater Reuse: Often the same code can be used across several very different sources of data (a classic example being your own database as one source, third party web service API's being others), with LINQ serving as a single point of commoonality.
Greater Interoperability: Many current .NET technologies work well with LINQ, and this will only increase. A LINQ-based approach positions projects to use these well.
Simple concurrency: Many LINQ methods are amenable to being quickly adapted to concurrent use where beneficial.
The nature of the data modelling provided by LINQ provides for great flexibility and scalability in an application allowing for more rapid development of new and enhanced functionality over the lifetime of an application.