The Kingston Is by far a more recognized brand, also hs better timing. That said performance wise, the ONLY diff between Cl 9and CL10 will be in benchmarks as you will see NO real world difference.
2 X 8 would preferable as as this would leave slots open for future expansion.
That said 1) If you are using win 7 Primium, then max memmory is limited to 16 gigs and to go above 16 would require a higher end Windows 7 ( windows 8 - Not sure if it has same restriction). 2) Currently only a select few apps can take advntage of more than 16 gigs.
MY choice would be:
1) Find a better brand of 2 x 8 and go with that.
2) Or stick with the 4 x 4 Kingston. Because of quality - NOT performance - as stated You will not see a performance diff.
MY favorite Ram Modules are G-Skill Ripjaws, or Corsair.