I think there is no need to turn it off if you don’t have a specific reason to do so.
For example let’s say you have 10 core cpu and 20 vCPU. If you will have 10 simultaneous tasks ( threads) in your system, the threads should be completed by physical cores with lowest time to finish the task. Let’s say those tasks are completed in 100ms.
If you have more tasks at the same time, let’s say 20 tasks. If you don’t have HT, the tasks will be completed in 200ms. Whereas, if you will have HT, cpu usage blocking will be optimized and it’s statistically results around 30% performance increases. So the task will be completed in 150ms (+-15ms)roughly.
So if you turn off HT, in case when needed, the CPU will be used more efficiently and your system will be faster. So there is no reason to turn it off.
But another use case can be virtual machines. If you give 2 vCPU to your 10 virtual machines and if CPU is shared not dedicated to each machine. The performance will vary for each VM. Or if a VM will have a vCPU, you can never know the performance will vary according to how busy are the cores of CPU. If your virtualization software supports, instead of giving one physical core to a virtual machine without HT, giving one core with two vCPU with HT will lead better performance if multithreaded software is used on VM.
So shortly, HT will not double the CPU power of the system, rather optimize it to get ~30% more power from it in case you will need more cores than your CPU has. But if you always use less simultaneous cores then the the number of physical cores, turning it on or off will not have any effect on your system performance.