Hard to say without knowing the requirements for the VM and why it was configured this way. IMO systems are often over-provisioned due to a software vendors requirements, which apply to physical systems, but may not necessarily be required for virtual environments. Another question would be whether other VM's run on the same host too and how overall performance looks like (e.g. CPU Ready Time)!?
Whether you use multiple vCPUs or a single vCPU with multiple cores doesn't really matter for performance, it's more a question of guest OS support and - in some cases - per CPU licensing.
André