Unfortunately, there are not a whole lot of head to head comparisons between the AXP-M and P-M. I can't do much better that restate what you probably know already:
*) AXP (3000+) will be quite a bit faster overall. A 1.4 GHz P-M would be in the ~2-2.2 GHz P4A performance range, the AXP would be more comparable to a (hypothetical) ~2.8-3 GHz P4A.
*) PM will have a noticably better battery life for equal battery capacity, especially when using low intensive stuff (light office apps, internet, ..) since AXP-M has a considerably higher standby power than PM. Using CPU/Harddisk/optical intensive apps (dvd burning, encoding, gaming, compiling,..), the difference would be less pronounced, but still very much a fact. Of course, battery life can always be traded with weight (higher capacity batteries), but if you want both (light and long battery), PM would give you a sizeable advantage.
*) you're more likely to find a nicely designed PM notebook than a AXP notebook. Choice is pretty limited with the AXPs, and especially in the "thin & light", there is a wealth of nice PM notebooks from just about any oem, and hardly any nice AXP based one's.
One thing though: if you decide for a PM based one, avoid the bundled "centrino" WLAN if you can. Its outdated, slow, and lacking essential security features like WPA. You're much better off with a third party 802.11g device, either built-in (if possible) or through PC Card. Its likely not even more expensive either.
= The views stated herein are my personal views, and not necessarily the views of my wife. =
There are two intel WiFI centrino solutions now - the original 802.11b and a new 802.11b+g. If you're after battery life I'd go with an intel wireless package as they have power saving features that are unmatched by any other manufacturer. The Broadcom 802.11b+g chip is pretty good as well, but uses noticibly more power.
I think WPA is more of a driver update then a hardware upgrade.
Also, I'm not sure how other people use their laptops, but everyone in our office just uses 802.11b for internet. When they want to move some serious data (ie: backups) they use cat5e as all our laptops have 10/100/1000.
*Dual PIII-800 @900 i440BX and Tualeron 1.2 @1.7 i815*
Thanks to both of you, this has been very helpful. I do hope they do some head-to-head type comparisons in the future, but at this point I think I'm going to go with the pentium-M. We plan to use this machine primarily for web surfing, e-mail, etc, with occasional gaming (mostly non-3d gaming at that).