I'd say go with either, the 260x can be faster in some games though, while the 750Ti is power efficient and will work with even some (good) 300w PSU's. I'm going to rock the boat though and say try to find a 270 on clearance though. Maybe even a 265, although those are rare.
Sometimes you can find a 270 (non-x) at prices equal to a 260x or 750 Ti, and you can overclock that 270 to the speed of a 270x.
If you have a microcenter near where you live, I'd say physically drive there and check out their clearance bins. Those deals are insane. You can find stuff like less popular GPU's (Gigabyte 3-fans, etc.) that are quite powerful, but priced the same as more popular, GPU's that are weaker. (270's priced the same as a 260x or 750 Ti).