I know this might seem a bit stupid but i know the 690 is a dual core card and the titan is single so its 4 cores vs 4 cores. Which one will perform better?
Absolutely yes. As others are saying, the titan is an unwise investment at this point, the 780 is a much more competent choice for a GPU. I assume you're not really making this as a purchase decision though and are just curious.
Do you really plan to make that purchase though? Because if so, is this you?
Both are crap as 4 GPU's don't work together, and the Titan is rendered obselete by the much cheaper and 7% slower 780. 1x 780 can overclock to easily mach a 690, and 690's don't really overclock at all.
You may want to consider some 780's, they are cheaper although a bit slower. But when you have even two of either card, it'll be enough to do anything. And you'll save $500 on the 780's. http://www.anandtech.com/bench/Product/764?vs=827