Timing - The time for which the RAM writes, reads or performs an operation.
To make it more clear, I will explain: DDR3 - 9-9-9-24 (The first digit is writing, the second digit is reading, the third digit is performing an action, the fourth digit is the life cycle of all operations.)
The timing parameters are shown to special lead us a little higher, but the DDR4 parameters are different. 9-10-10-24 It is because of such a seemingly insignificant parameter that DDR3 wins if they have the same frequency.
After looking at the comparison of RAM, you probably still have a question, but what is better to buy and where to use?
The answer to this question is as follows: DDR3 RAM is already outdated and it is not worth buying, unless you are not going to use old processors. Since DDR4 is relevant only for processors from the 6th generation (Intel) and Ryzen (AMD), it will not work on older ones.
However, you need to understand that all the juices have been squeezed out of DDR3 and it is no longer better to do it, and if you are going to use demanding programs and the speed of your PC is important to you, then it is better to spend a little more money and buy DDR4.
Recently, DDR4-type RAM has become even a little cheaper than DDR3 because the latter is difficult to find.