A Pentium M does not have HT. A Pentium 4 has HT. A processor that has an extremely long pipeline like the Pentium 4 is capable of using HT. A Pentium M with a small piepline cannot use HT because of lower clock speeds. However, a lower pipelined processor is much better. HT is not critical, but it improves performance on a processor like the Pentium 4 by 5-10% which is a large gain. It helps to execute two threads at once and this really helps.
A PM is a better processor for gaming. Think of it as giving similar performance and having similar weaknesses and strengths like the AMD Athlon 64 family. The Pentium 4 is better for power apps and really has no competitors in that arena. I'm giving my DAD my P4 cause he is going to use it to run SQL/Oracle and other database apps. I'm getting a Pentium M myself and am going to oc it and use it for gaming and animation and photoediting and web design.
P-4 with HT vs. P-M with HT 
Linear Mode
