Notebook video card differences? Help on the right one

Does anyone have an idea on the differences between comparable systems equipped with 32MB ATi Mobility Radeon 7500, 64MB ATI Mobility RADEON x300, 64MB dedicated to video, and no video card at all?

I just need a list of which would be fastest for graphics/word processing and how big of a gap there is between the different options.

I am trying to build a very economical, thin and light laptop with great battery life, but I also want the best performance available. I am looking at 14.1" screens with a weight of around 5 lbs. I really like the IBM Thinkpad T42(32MB Mobility Radeon 7500) but I am unsure of just how the video card will perform. I like the how light it is(4.9lbs) and how thin it is(1"). The T43 is its larger cousin(coming in at about 5.7 lbs, 1.2" thick) which features the 64MB Mobility Radeon x300. I am also looking at the Dell Inspiron 600m(coming in at 5.6 lbs, 1.3" thick), which features 64MB dedicated to video, but I have been unable to find the chipset that it uses(I assume some type of Intel one). There are also some smaller ones I have been considering that have nothing dedicated to video nor a card.

I don't plan on using the notebook for any type of gaming, but I do want to be able to do business/student type of things very quickly.

Which of the video cards is the best? Which of these notebooks fit my needs the best? Are there any others that could be recommended?

Thanks so much for any help. I have been doing loads of research and learned a ton, but I haven't run into any numbers or comparisons between video cards.