dynamic keyword vs object data type

One variable is typed as object by the compiler and all instance members will be verified as valid by the compiler. The other variable is typed as dynamic and all instance members will be ignored by the compiler and called by the DLR at execution time.

It has nothing to do with either performance or memory allocation. The dynamic type is a static type that the compiler somewhat ignores. It gives you the ability to use duck typing in a statically typed language which provides a lot of flexibility (especially when dealing with components written in languages that are more dynamic).

I would definitely recommend that you read up on the following topics:

• dynamic (C# Reference)
• Using Type dynamic (C# Programming Guide)
• Dynamic Language Runtime Overview