The second one, the one with the link, is a command line version which means no icon in menu but advantage is that you can invoke from script better.

There are two issues you might run into : Making sure it tries to connect -after- the wireless has connected to wlan... you might need to find a way to wait 10 seconds and then launch. Also rdesktop frequently fails on first attempt for me so not sure if it will always connect first time.

Since your script will not be visible, you wont be able to see any errors... unless you redirect output to file.

If your using that second command line version you might try a script file like this :
#!/bin/sh
rdesk -f -u username -p password -z 192.168.1.100

replace username and password and ip and set execute permission on script (chmod 755 myscript.sh)

And finally i havent gotten this to work so im still just guessing thats how it works... i might try again later but alot of times the first connect fails for me and i have to connect twice.... maybe repeat the rdesk command twice and ignore/close if two windows appear?