Extract from http://www.webopedia.com/TERM/S/SMP.html
(1) Short for Symmetric Multiprocessing, a computer architecture that provides fast performance by making multiple CPUs available to complete individual processes simultaneously (multiprocessing). Unlike asymmetrical processing, any idle processor can be assigned any task, and additional CPUs can be added to improve performance and handle increased loads. A variety of specialized operating systems and hardware arrangements are available to support SMP. Specific applications can benefit from SMP if the code allows multithreading.
So I think that processors with HT can benefit from this performance boost.
The other one, w/o the smp ending, is the standard kernel, without the HT support, I think.