Well HT is all logical. HT tricks windows into thinking 2 CPU's exsist. Windows then sends 2 threads to the CPU. HT allows 1 thread to be halted and let the other one go really quick, halts that one, and lets the other one go. so on and so forth.
Dual Core is like having 2 cpu's but on 1 CPU. So you will be able to run 2 different threads at the same time unlike HT. Dual Core technology is physical.