arcgis desktop - Difference between Copy Features and Feature Class to Feature Class tools?

I have a feature class within a feature dataset in a file geodatabase (FGDB), and I need a copy of it in another FGDB.

In ArcGIS 10.1, I've used the "Copy Features" tool, and it looks to be the same (according to the "Feature Compare" tool). Using the "Feature Class to Feature Class" tool, I receive the following messages from "Feature Compare":

Field: Field OBJECTID domain fixed is different (Base: false, Test: true).
Field: Field Shape domain fixed is different (Base: false, Test: true).

Does anyone have any insight on the differences between "Copy Features" and "Feature Class to Feature Class"? What do the messages from Feature Compare mean?

Answer

The Feature Class to Feature Class tool is a Conversion tool. The idea is to convert a feature class in one format (e.g. shapefile) to another (e.g. geodatabase). It also allows the user to control the Field Map - i.e. which fields will be copied over.

The Copy Features tool simply creates an exact copy of the input features. Note - this tool can also be used for data conversion but cannot be used to manipulate the Field Map.