I wouldn't bother picking between 1333 or 1600, whatever is cheapest or highest capacity. Going above 2000mhz makes a difference. My rule is always capacity over speed, within reason.
I ended up 16GB of 2400mhz stuff because RAM was cheap when I bought... it goes through cycles, if it's cheap, don't delay if you can afford. Waiting you may pay more. On the flipside, if it's too expensive... just wait.
Best to look and see where the price cycle is