Confusion with CPU Memory Specifications

[James1989]

Looking into building a custom PC and was just curious about CPU Memory Specifications regarding what type of RAM should be used and Memory type.  Also the CPU I was thinking of getting is a toss up between the i5-6600k for $249.99 or the i7-4790k for $299.99 (this is in U.S. dollars).  The confusion comes should I pay more attention to what the motherboard specs are or what the CPU specs are in regards to using DDR3 or DDR4.  Thanks for any help you may give.    

[KingUnicorn]

the main reason you want to focus more on the mobo specs is because you need to know what channel the memory runs at. some boards run at quad channel while others run at dual channel. for the cpu it's generally a case of if it's ddr3 or ddr4 (or ddr3l or ddr4 for skylake CPUs). most base clocks for memory is supported by basicaly all CPUs.