For highly optimized workloads (e.g. x264 video encoding or raytracers) I've seen about the same 20-25% increase at most. On general heavy and diverse workloads

For highly optimized workloads (e.g. x264 video encoding or raytracers) I've seen about the same 20-25% increase at most. On general heavy and diverse workloads the number is rarely ever above 5%, while the power consumption and the security concerns run off all the same. I personally disable SMT on everything I can.