When I try to copy or move folders with names that conflict with existing folders, I get an option to Merge or to Skip.
Sometimes I want to really replace the folder entirely with the new one, and not end up with a mixture of new and old files.
For example, if the same folder exists on two computers, and I have just cleaned it up and made some changes, I want to be able to replace the older version on the other computer.
I do not like solution 1-3 because I consider "Replace" to be dangerous for whole directory trees with its implicit "delete first" (especially for first-click-then-read-people like me ;-). In such a cases I prefer to delete and copy/move separately.
@maxwell69: I do welcome solution 4! And I think that this deserves an own idea. Mutli-threaded copying to/from the same harddisk is a bad idea even with the cfq or deadline scheduler. So please open an new idea for that.
Back when I had my Amiga an option when copying from one folder to another was "only replace with newer files". This was very very useful for me. I think this should be an additional option with copying.