well basically they are different dashes. They will all cover the basics, but some delve into more specific areas, so over time (depending on your interests) you will use a number of different ones.
Ndure is a handy one when hotswapping: you can FTP to it, and its got a nice file browser. From this I FTPd XBMC onto my xbox's.
Ive mainly mucked around with XBMC and its run all the Apps, games etc ive thrown at it. If I choose to run a game off a disk, i pop open the dvd tray, and put the disk in. Once it closes it autoloads the disk as normal. If I want to run a not so legal copy of a game, I use the "programs" channel on XBMC and set its source to F:\games. In that folder I put my games (ie. F:\Games\Halo 2\<files for halo 2 go here>).
Then my apps channel will have an icon for Halo 2 and when i select that, it loads the game. Similar scenario for any apps u want to use.
All dashes should load .xbe files, which you will find on a game CD or on a game backup as a default.xbe file. So if you put ndure on your xbox, and load up the filebrowser on ndure, you should be able to navigate your way to the default.xbe file and load the app/game.