-copyFromLocal is similar to -put command, except that the source is restricted to a local file reference.
So basically, you can do with put, all that you do with -copyFromLocal, but not vice-versa.
Similarly,
-copyToLocal is similar to get command, except that the destination is restricted to a local file reference.
Hence, you can use get instead of -copyToLocal, but not the other way round.
Reference: Hadoop’s documentation.
Update: For the latest as of Oct 2015, please see this answer below.