That is the important point; Lenovo has effectively merged the 2 products so that they can be configured identically; it is the model number (3 digit) that counts, and not the T61 vs. T61p distinction. The chassis always was identical, but in the past the p series had big hardware differences; these are gone now. Both excellent choices.

The screen resolution (and quality) is an important consideration. Each of the available screen choices has a difference and if you are picky then it matters a lot. My personal favourite is the original 1400x1050 display, which is gorgeous, but some people cannot stand it. Now I would only buy the 1200x1600 (or 1920 in widescreen)because I really need the screen real estate. For mobile use, the 15.4 inch is a lot bulkier than the 14.1 -- amazing the difference an inch makes.

As for the battery life comments on this thread, they are true for XP but less true for Vista. One of the big improvements in Vista is power management (much of it due to the new driver model), so some of the high power graphics mobile chipsets will run in low-power mode for "desktop" use. Doubles the battery life. Turning off Aero increases it even more. My new Vista notebook really surprised me with the increased battery life, it wasn't something I expected.