VPP dev here. Our perf tests for Intel run in CSIT lab consistently shows a perf benefit of 10%-20% since Haswell I believe, so in our typical VPP deployment we usually map 2 VPP workers (dataplane threads) to both hyperthreads of the same physical core. But that's for VPP, your mileage may vary depending of your workload (eg. FreeBSD kernel stack).