You gotta differentiate between "Quad Channel" as a performance term and "Quad Channel" Memory Kits.
No difference between what you listed, just the RAM manufacturer tested the 4 Modules together and approved it, gathered it in one set.
Same for the other set, the manufacturer tested the Dual Channel kit and approved it works great together.
Better wait for the best x79 RAM kit review from Tomshardware, they promised a sooner review when they reviewed the i7 SB-E 3960X.
I've never seen enough difference to pay a premium. I'll have to check out the x79, but my answer would be the same. For me, it's still a marketing gimmick just like some of those pretty heatsinks. If you check the timings between some of those pretty kits, they are virtually the same. Just $15-20 more.
Does he mean dual rank vs quad rank? Multiple sticks of quad rank causes the memory bus speed to drop down due to performance and buffer issues with memory management onthe processor. Multiple sticks of dual rank memory do NOT cause the memory bus speed to drop down.
Multi-channel memory architecture is a technology that increases the transfer speed of data between the DRAM and the memory controller by adding more channels of communication between them. Theoretically this multiplies the data rate by exactly the number of channels present. Dual-channel memory employs two channels which theoretically doubles the data transfer rate. The technique goes back as far as the 1960s having been used in IBM System/360 Model 91 and in CDC 6600.
Modern higher-end chipsets like the Intel i7-9x series and various Xeon chipsets support triple-channel memory. On March, 2010 AMD released Socket G34 and Magny-Cours Opteron 6100 series processors which support quad-channel memory. In 2011 Intel released chipsets that support quad-channel memory for their LGA2011 platform. Historically, microcomputer chipsets with even more channels had been designed. For example, the chipset in the AlphaStation 600 (1995) supported eight-channel memory, but the backplane of the machine limited operation to four channels.