I'm going to use the Asus Crosshair IV formula and I'm very curious to find which RAM is suitable for my needs. I find not much difference between these two and just to make sure i buy the correct one i need. So what would you recommend me?
ddr3 1600 if you want the extra bandwidth, but ddr3 1333 shows *very-close* performance in real world applications. your choice, but most people go with ddr3 1600. you could always downclock it and tighten the timings of 1600 - 1333. and yes ddr3 1333 is cheaper.
also note that higher cpu clock will give more of a performance boost in memory even when using lower bandwidth. you could shave off some $ from your memory and use it on a better cpu OR gpu which will have more of an effect on performance than your memory will.