which superkey/pass?

Either

Super Key

http://www.cheapmod.net/item--Super-...rder--superkey

or

Max Media Launcher

http://www.cheapmod.net/item--Datel-...atelmmlauncher

This would be going with a EZ4-Lite for for NDS Lite.

Whats the main differences if any?

You can't use them with EZ4-Lite, if I remember. You need EZ4-s Passthrough to use it.