The answer is, of course, "it depends." Heavily threaded floating-point workloads, for example, will see a ton of contention and performance degradation on the 6200-series Piledrivers because there's one floating-point unit for every processing core. The 6100 series doesn't have this limitation, but IIRC they still have some perf wonkiness on some loads.
There are also power concerns with the AMD stuff, which matters a lot more in data centers/"cloud" environments than it necessarily does in a desktop.
A lot of server workloads (mail, web, database, most apps) are pretty light on memory bandwidth, so 16 cores sharing memory bandwidth isn't necessarily an issue.
Cache contention/invalidation is probably the bigger potential issue. I don't have a lot of experience with server VMs and I don't know how smart (or dumb) they are about pinning things to particular CPU cores in order to minimize cache issues.
