C#: System.Object vs Generics

Always use generics! Using object's results in cast operations and boxing/unboxing of value-types. Because of these reasons generics are faster and more elegant (no casting). And - the main reason - you won't get InvalidCastExceptions using generics.

So, generics are faster and errors are visible at compile-time. System.Object means runtime exceptions and casting which in general results in lower performance (sometimes MUCH lower).

A lot of people have recommended using generics, but it looks like they all miss the point. It's often not about the performance hit related to boxing primitive types or casting, it's about getting the compiler to work for you.

If I have a list of strings, I want the compiler to prove to me that it will always contain a list of strings. Generics does just that - I specify the intent, and the compiler proves it for me.

Ideally, I would prefer an even richer type system where you could say for example that a type (even if it was a reference type) could not contain null values, but C# does unfortunately not currently offer that.