MSTSC and RDP

MSTSC is RDP actually ;-)

What is the difference between MSTSC and RDP?

No difference if target is XP or Vista
If you append /console in RRP client, that's the same as MSTSC /console

..and difference if targeting Win2003, /console connects you with the interactive session of that server, while without /console you will get a separate session.

Syntax
MSTSC option
MSTSC /Edit"ConnectionFile"
MSTSC /migrate

Options
ConnectionFile: the name of an RDP file for connection

/v: The remote computer to connect to

/console Connect to the console of a server (NT/XP)
/Admin Connect to a session for administering the server(Vista/2008)

/f Start in Full Screen mode

/w:width Width of the RDP screen
/h:height Height of the RDP screen

/span Match the Remote Desktop width and height with the local virtual
desktop, spanning across multiple monitors if necessary.(Vista/2008)

/public Run Remote Desktop in public mode. (Vista/2008)
In public mode, passwords and bitmaps are not cached.

/edit Open the RDP file for editing.
/migrate Convert a legacy Client connection file into an .RDP file

The /console option only works when connecting to an Windows XP Professional or Windows Server 2003 computer. When connected to a remote desktop, the key combination Ctrl-Alt-END will send Ctrl-Alt-Del to the remote client.

Examples:

MSTSC /v:MyServer /f /console
MSTSC /v:127.0.0.1 /w:1024 /h:768
MSTSC /v:MyServer /w:800 /h:600
MSTSC /edit filename.rdp