Question Memory latency with ryzen 3900x

[Aaron Connor]

Looking at a ryzen 3900x build not sure what memory to go for:

Size / Capacity	32GB (2x16GB)
Memory Model	Vengeance LPX Black
Max. Memory Channels Provided by Kit	Dual (2)
Memory Type	DDR4
Memory Type (ECC)	Non-ECC
Memory Type (R/U)	UDIMM (Unbuffered)
Memory Speed	PC4-28800 (3600)
Pins	288
Memory Ranks
CAS Latency	18-22-22-42
Voltage	1.35 V

or

Size / Capacity	32GB (2x16GB)
Memory Model	Vengeance LPX Black
Max. Memory Channels Provided by Kit	Dual (2)
Memory Type	DDR4
Memory Type (ECC)	Non-ECC
Memory Type (R/U)	UDIMM (Unbuffered)
Memory Speed	PC4-25600 (3200)
Pins	288
Memory Ranks
CAS Latency	16-18-18-36
Voltage	1.35 V

I really don't get the CAS Latency thing.
Thanks for any advice.

 

[Aaron Connor]

so having done a little research the cas latency is the same for both using latency/speed*2000 both = 10 nanoseconds so does it really matter?