Difference b/w My.Computer.FileSystem & System.IO.Directory

Question

What are the differences between My.Computer.FileSystem and System.IO.Directory

Iam using My.computer.FileSystem in my existed application to do some IO operation such as getfiles, copy files, move files,delete files.
Instead of getfiles i want to use enumeratefiles method but enumerate is not present in my.computer.filesystem so i wanted to replace it with System.IO.directory .

 Is there a performance difference?
 Pros and cons ?