for one thats only 2 sticks so dual channel and second its 2400 @ CAS 16 (ew). Now the difference isn't big enough to matter but why not have better overclock abilities and said benfits for $50?
edit: now if the ops wants to go the cheapest 32gb route, than yes that would be the best choice. Gskills 32gb (same specs) kit is $333.
Yeah, if he wants 32GB then picking up two of the ones IVI recommended is the way to go. If he only wants 16GB and quad channel, it's best to get a quad channel kit for that. If you're already planning to go the X99 route, why stay with dual channel RAM when you can run quad? Eight total DIMM slots on the board, so better to go with four sticks at the start and see where that gets you.
The Kingston kits linked earlier would be a great set thanks to the tight 13-14-14 timings and 2666Mhz speed bin. More so than the Ballistix set linked which are 2400Mhz Cl-16.