Looking at the latest G.Skill series it looks like:
- ARES, RipjawsX, Sniper = the same IC , the same specs, different heatsink ( I made ARES and RipjawsX 2133/2400 tests based on the same IC )
- RipjawsZ = mixed IC , most new are Hynix but some top series ( black heatsinks ) are also on Samsungs or blue 1866 were on Micron
- TridentX = probably the only memory that up to 2400 clock has everything on Samsung ( above 2600 all is Hynix )
Going back to ARES/RipjawsX/Sniper, I had biggest luck with ARES kits even though all supposed to be on the same IC.
Here are tests of 2133 RipjawsX and 2400 ARES. Both on the same IC. Both OC about the same and both can find as 2133 10-12-12 or 2400 11-13-13. New Snipers or RipjawsZ 2133 10-12-12/2400 11-13-13 will be acting the same.
http://www.overclockers.com/forums/showthread.php?t=734805
http://www.overclockers.com/forums/showthread.php?t=737385
I still have to check how ARES 2133 9-11-10-28 is acting on ASRock Z87M. It was running 100% stable @2666 11-13-12-34 1.65V on Z77 boards but I couldn't make it run at the same settings on a Gigabyte Z87X-OC.