Intel.com wants to keep you in the Intel camp so they have good descriptions of what their cpus can do at www.intel.com
The Pentium 4M was really never intended for a notebook but they got put in (4M is notebook modified version of desktop Pentium 4 with some power management improvements but not much) as people wanted portable power.
The only reason to get a hot and heavy Pentium 4M now is if you need the hyperthreading multitasking function (Pentium 4M's that indicate they have HT or hyperthreading) which will give you somewhat better performance if you multitask heavily (have more than 5 programs open all the time and switch between them frequently).
Otherwise, you are better off with a Pentium M (Centrino) even if you use it only occasionally unplugged. Once you have hooked up to a wi-fi router (under $50 and 54G minipci card is standard on nearly all notebooks over $1,000) you will want to move around the house and even sit in the backyard or porch or in front of the TV or on the kitchen table) without having to turn off the notebook or have wires.
Note that a Pentium M 725 1.6 Dothan or higher (with full 2mb L2 system cache on the cpu to make faster access than the RAM or hard drive) will perform at up to 2x its clock speed so a Pentium M 1.6 can be compared to a Pentium 4M 3.0 ghz except for hyperthreading.
A Pentium M (Centrino) with an 8 cell battery (don't get suckered getting a 4 cell battery like on some Acers which cuts your battery life in half) will get 3.5-5 hours battery life. Most Pentium 4M's will get about 2 hours or perhaps 2.5 unless they have a monstrous 12 cell battery that is very heavy (some Toshiba Pentium 4M models have a large battery and get very good battery life but they are hot and heavy).
Note that neither of these is 64 bit like the Athlon 64 so you should consider that expecially over the Pentium 4M as it is 64 bit and will run faster when Windows Longhorn arrives in 2006-2007. HP/Compaq and Gateway/E-machines have Athlon 64's and you very well might find them the best choice if battery life is not your #1 priority.
When low voltage AThlon 64's arrive in 2005 then Pentium M Centrino users like me will take notice but until then for an all around efficient notebook (size, weight and battery life) the Pentium M is tops for that camp right now.
I am looking forward to purchase a notebook and I would like to know the difference between the centrino and pentium 4 processor. Which is the better processor in a notebook. I intend to use the notebook at home as a desktop replacement. I may travel occasionally with it. Can anyone help with the benefits and disadvantes? Or point me to a technical information anywhere on the internet?

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