Hi,
Basically, the higher the mhz the better but the lower the timing is the better.
Between 1333 and 1600, their is almost no difference.
The bigger difference would be a 1333 with cl11 would be slower while 1600 cl8 would be the fastest.
But your talking about a few milliseconds.
Gaming pc or not.
The last think too look at would be the price: 2 gb 1333 cl 9 @ 50 $ would be better than 1600 cl8 @ 100 $ (not much difference between them.
BTW I upgraded 4 gb 1066 cl 8 to 8 gb 1600 cl8 and changed windows experience by .4 (7.4 to 7.9) No difference in boot / gaming ect.
I guess the only difference would be in encoding huge files. You could get a few minutes less there.