Memory for Servers DDR4

Memory for Servers - DDR4 ECC 16gb
Memory for Servers - DDR4 ECC 8gb
Memory for Servers - DDR4 ECC Registered 16gb
Memory for Servers - DDR4 ECC Registered 32gb
Memory for Servers - DDR4 ECC Registered 64gb
Memory for Servers - DDR4 ECC Registered 8gb

How do I decide on which components are good or better than others ? How do I decide the best buys.

First and Foremost we can google the product we wish to buy and check it's reviews or what others experience about the component you wish to buy. You may also post your queries on any of technical forums and get replies from other users.