GTX 750Ti OC version is really an awesome BUDGET gaming graphics engine. I will recommend this card to the people who really can't invest a more of its real cost. At the same time, you must know that this card is not going to come in handy when you want to play the today's and next-gen games with ULTRA GRAPHIC SETTINGS. You might need to turn off the shadow, set the AA to the most lowest value, keep the graphics quality to LOW/MEDIUM and so on. Overall, this card is not going to help you to play upcoming games in a good quality yet could do things in low-medium settings which will upset you down the line.
R9 270X. Really a fantabulous,commendable and inexpensive graphics card in which the high performance and quality are being clubbed. Like I always use to quote, it's a "bang for the buck" card. It is really a nice graphics engine and capable to play today's and upcoming games in ULTRA HIGH graphic settings. AMD has proved its expertise from this least expensive card. Yet, you may/may not need to tweak a tad of settings to experience the full power house of the card and it is negligible at most of the times. I have overclocked my r9 270x through CCC and it perfectly works for me (still testing, though). Overall, this card is capable to play the games in ultra settings for sure yet you might have to tweak a few.
Wanna be a gaming enthusiast? Not worrying about your budget? Then, go with R9 290 / R9 290X / R9 280X / GTX 780 Ti / GTX Titan. These are the like king makers of the graphics card world. But, they are known to be very expensive computer component in our country. Here, I didn't mean R9 270X is worse. The enthusiast cards are tad superior yet 270x can play games in ultra. When it comes to expensive graphics card, you really don't need to tweak few settings like you may/may not do it for r9 270x.
As a conclusion, the decision is in your hand, OP. If you do not want to break your budget and play all games in ultra settings, then you can definitely choose R9 270X. Otherwise, R9 290X is the right one for you to rule the gaming world but hard to afford (provided you have financial constraint).
Note: In the meantime, look below for top graphic card brands -
> Sapphire
> MSI
> EVGA
> XFX
Reason => they make cards with good build quality which can sustain manual overclocking.