Long story short, if they are the same price get the R9 270x, but it doesn't matter really cause you will never reach that level.
If it is even a dollar more, I wouldn't bother. Dazinek is wrong when he said an R9 270 is basically a 7850 while an R9 270x is basically a 7870. The R9 270 cards are nearly identical, they both have the same number of shaders, same amount of ram, same amount of bandwidth. The only thing between them is usually about 100Mhz. Which means the R9 270x is 10% faster but purely because of clock speed. They bin the chips, so higher quality chips end up in the R9 270x so they will more reliably overclock higher, but the R9 270 can overclock close to the same and the difference is really small. There isn't really any valid reason for them being two separate cards.