I guess that is the bottom line with so many variables of our systems.... try it both ways and see what works best for you?
 
Jim
 
PS - which was the crux of my original advice to the OP

eikelbijter
So much fail in these responses......WOW!
 
First of all, while it is true that a 4GHz single core would outperform a 2GHz dual core, in a modern OS with a modern application like Sonar, multi-threading works quite efficiently, especially in inherently parallel tasks like a multi-track DAW.
 
What happens with HYPER-threading is that the CPU is allowed to process two thread on 1 core, using different parts of its pipeline at the same time (think Floating Point versus Integer). It certainly doesn't double the performance of a core, but can lead to 20% more throughput. There IS more scheduling overhead, but not very much and the performance increase in highly mixed workloads is noticeable. For instance, the screen rendering parts of Sonar are very much integer tasks, while calculating plugin processing is highly Floating Point based.

I guess you did not bother to read them all of the responses.  My advice was to turn it on

abacab

eikelbijter
So much fail in these responses......WOW!
 
First of all, while it is true that a 4GHz single core would outperform a 2GHz dual core, in a modern OS with a modern application like Sonar, multi-threading works quite efficiently, especially in inherently parallel tasks like a multi-track DAW.
 
What happens with HYPER-threading is that the CPU is allowed to process two thread on 1 core, using different parts of its pipeline at the same time (think Floating Point versus Integer). It certainly doesn't double the performance of a core, but can lead to 20% more throughput. There IS more scheduling overhead, but not very much and the performance increase in highly mixed workloads is noticeable. For instance, the screen rendering parts of Sonar are very much integer tasks, while calculating plugin processing is highly Floating Point based.

I guess you did not bother to read them all of the responses.  My advice was to turn it on

Did I say there was nothing but fail?

Intel reckon there's at least a 30% cpu throughput increase with hyperthreading. It certainly won't slow down any core to less than it's rated speed.

What hyperthreading does is improve multi-tasking, and with a modern operating system or DAW even if you are only using one application there is still a lot of multi-tasking going on 'behind the scenes' as a look at the processes list would tell you.

It makes better use of less than fully-laden cpu cores so shifts things through the cpu faster, simple as that. It won't necessarily save you from running out of resources, any system can be pushed to the point it can't keep up, but it helps to make that point further away and keep things running more smoothly by optimising core usage.

And if for some reason it slows down your PC, then turn it off again. Personally I find things work better in terms of total cpu load with hyperthreading enabled, but there's so much variation in Windows PCs that may not be true for all.

HT was not recommended in XP.  Usually Intel is far ahead in tech than a Windows OS. I had a P4 Prescott that had it. I would use it in W7 and above. 

Hey!!!
LTNS kite

it's easy to see HT benefits, just compare pentium with i3
http://www.cpu-monkey.com/en/cpu-intel_pentium_g3430-59
http://www.cpu-monkey.com/en/cpu-intel_core_i3_3220-390
 
3.3 GHz and 3MB L3 both