Hey Rtech,
Firstly, serial port.......ummmmmm...... its been so long since ive used one of those that i dont even know what it is anymore!
(ok thats an exageration) but believe me, you will never need one unless you have some really old peripherals which you plan to use with your new laptop.
EVERYTHING is USB and Firewire these days. (So what you should also look at is the number of USB ports as well as check if a firewire port is available.)
Personally i like the matt black finish of the IBM as well, its just their design, design functionality and styling that i find ugly, atleast on the R31.
Heres another question, do all the laptops have a 5400RPM 40GB?, remember more RPM = more bhp, faster seek times and higher data bandwitdh.
I guess the question you have to ask yourself is whether you want that extra 1" of screen or you want a lighter laptop etc etc.
They seem so similar that its totally a matter of choice.
R