Multi-core vs Multi-CPU
This question is very broad, and the answer depends very much on the nature of your workloads and your planned SQL Server setup. However, assuming your future hardware supports NUMA (why wouldn't it?) and given that


  With SQL Server 2016 (13.x), whenever the SQL Server Database Engine detects more than eight physical cores per NUMA node or socket at startup, soft-NUMA nodes are created automatically by default. [...] the SQL Server Database Engine creates soft-NUMA nodes that ideally contain eight cores


one might reason that the vendor thinks 8 cores per socket is the optimal configuration in most cases.

You might also find this old article useful.