If your budget will allow I think you will be happier with the MSI Twin Frozr IV GTX 670. It is 270 instead of 230 for the MSI Hawk r9 270x but you also get assassins creed black flag and splinter cell blacklist with the gtx 670. If you look at it this way, MSI hawk r9 270x (230) + Assassins creed black flag on steam (60) + splinter cell blacklist on steam (60) = 350 dollars vs GTX 670 (270) and both games FREE the 270x ends up being 80 dollars more expensive if you look at it from this angle.
The GTX 670 is only a tiny stones throw away from the performance of the gtx 680/gtx 770. It basically sits in between the gtx 760, which it is more powerful than, and the gtx 770, which it is very close to performance in. Basically a maximum overclocked gtx 670 can equal the performance of a stock clocked gtx680/gtx 770 and even exceed it in some cases. It's a very good price/performance ratio card. The GTX 670 consistently outperforms the r9 270x to varying degrees. Sometimes the difference is only 4 or 5 fps but other times it's 20-30 fps (or even more) faster but at every single game used as a comparison the gtx 670 was always the winner by some margin even the most radeon optimized game the 270x still loses to the gtx 670.
Even with the higher performance of the GTX 670 power usage is virtually identical. Some situations the gtx 670 uses more and some the 270x uses more, it's basically a wash. Same thing with the temps as well. Since both cards use a similar twin frozr setup with similar fans they are both quiet cards. Since nvidia is just able to offer better performance with more efficient use of its power you get more fps and higher performance without a power or noise penalty.
It's all win win win from every perspective. Higher FPS and greater performance while keeping the power and noise practically identical to the 270x. And while the card may be 40 dollars more you get 120 dollars worth of games for free the latest and greatest Assassins creed IV and Splinter cell. I feel it's a no brainer. Just skip taking the wife/gf out for dinner one day and grill some burgers at home or skip going to the bar for sunday night football and buy a 6 pack and watch at home or something and you just saved the 40 dollars needed to get a much nicer gpu and you score 2 brand new triple a games in the process as well. And while this may be controversial in my opinion nvidia hardware is more reliable and better built than radeon hardware. As well as the drivers wrote by nvidia are more stable and just better all around and cause less problems than radeon drivers. And last but not least if you haven't looked up this new feature on the horizon called G sync it is going to be game changing (no pun intended). It will sync your monitors refresh rate in real time to the fps output of your card. This means the annoyance of screen tearing is FINALLY gone without having to take the performance penalty and other downsides of Vsync. You will need a new monitor with the gsync chip installed in it but it is totally worth it, nvidias demo of the tech was mind blowing and made games look so butter smooth even with fps's in the mid 30's
I hope I successfully made my case to you. I'm positive that extra 40 cash will be well worth it. And I'm not sure how the free games are distributed but you may even be able to sell off your download codes for the 2 games on ebay. Since the games are selling for 60 on steam if you put them up for 40 each they would sell in no time so now you only pay 190, 40 dollars cheaper and better in every way. I don't see how you can still choose the 270x over the gtx 670 after hearing all these facts.
Good luck with your purchase, I know you will do the right thing.
First off: Where are you getting a GTX 670 with a respectable, silent, cooler for $270? I know the ASUS coolers, as reviewed by SPCR are up to snuff, but they're 323$ on amazon while a MSI R9 270X is 200$ on Newegg. It's a completely different price segment.
Also, it's foolish to value the games at 120$. Assuming you even want to play the games in the first place, their running price on ebay is 10$, simply because of the fact that so many are available because so many people don't want to play the games they got through their Nvidia card. And even if you valued the games at an absurd amount above their actual value, the AMD cards come with their own game bundle as well. However, when you're on a forum valuing silence and power consumption, I think the small game bundles should be an afterthought compared to the noise/power consumption/price of the card.
I'm not saying the 670 is bad, but it's a completely different price segment. It's kind of pointless and foolish to compare the two and say that the 670 is strictly better. If you want a 16% performance gain and a proven, SPCR appraised cooler for $123 more, go for the 670. Otherwise, get the R9 270X.