Not really sure what you're asking here.
You want to know the best procedure is for grabbing the last chat message?
I do believe they all do the same thing.
If you want to get text from anywhere in the chat box (eg. username) I would suggest using a simple IsTextAt/IsTextAtEx
Here's what I used for my responder:
SCAR Code:
if(FindText(x, y, Players[CurrentPlayer].nick, SmallChars, 9, 412, 113, 433))then
begin
Exit;
end
else
Edit:
Oooh, nice idea there, Smartz 
I guess I should probably update our autoresponder then... (Yes, I know. I haven't touched it for a while. [It is weird to look a script I made a long time ago. Boy, I didn't know much back then
])