Debugging - It is really very hard to debug the Stored procedure but as LINQ is part of .NET, you can use visual studio's debugger to debug the queries.
Deployment - With stored procedures, we need to provide an additional script for stored procedures but with LINQ everything gets complied into single DLL hence deployment becomes easy.
Type Safety - LINQ is type safe, so queries errors are type checked at compile time. It is really good to encounter an error when compiling rather than runtime exception!
Built-in security - One reason I preferred stored procs before LINQ was that they forced the use of parameters, helping to reduce SQL injection attacks. LINQ to SQL already parameterizes input, which is just as secure.
NOTE: If all you're doing is simple INSERT, UPDATE, and DELETE statements LINQ is the way to go (in my opinion) and all the optimization is done for you, for more complex work I would say to stick with stored procedures
