The GTX 660 Ti would be faster than the 750 Ti but I agree with Seladon, you should go the R9 270 route but instead of the MSI, Sapphire is the best manufacturer of AMD cards. Go with the Sapphire R9 270 Dual-X http://www.amazon.com/gp/product/B00I0D81OG.
Sapphire has the best warranty and support in the AMD market. Their cards are very reliable, have great cooling, and overclock quite well also.
The GTX 660 Ti will perform faster, but will cost almost twice the price, and will need more power. I'd go right between those two and get ->this card<- which will do great in both of those games.
The GTX 660 Ti would be faster than the 750 Ti but I agree with Seladon, you should go the R9 270 route but instead of the MSI, Sapphire is the best manufacturer of AMD cards. Go with the Sapphire R9 270 Dual-X http://www.amazon.com/gp/product/B00I0D81OG.
Sapphire has the best warranty and support in the AMD market. Their cards are very reliable, have great cooling, and overclock quite well also.