The 780Ti is quite a lot better than the 780
But is it worth 200$? Honestly, i wouldn't go with Nvidia, Because the 780 was 700$, and then amd released the r9 290x, and they dropped it 200$. I personally dislike the company, because they were sucking off consumers, when they could have been selling it for the price it is now.
My opinion, and it is why I go with the company selling things at real prices.