I seriously doubt that the 22% speed increase has very much to do with the DDR4 memory.
It's really almost impossible to compare DDR3 vs DDR4 on an even level, as nearly all other components will be different as well.
When I built a new PC a year ago, the general consensus was that DDR4 is certainly faster, but in the real world, you probably wouldn't notice the difference. At the time the price difference was more than double.
I went with the DDR4 platform because of the affordable 6 core processor, not because of the DDR4. It's nice to see 12 cores (with hyperthreading) running at 100%.