You really can get this information from Google. A bit of effort on your part will go a long way... But, for the sake of enlightenment and since I have the urge to type (having just bought a bluetooth mouse/keyboard combo for the MBP at work) here goes:
Get the new models. Specifically the 2.2 Ghz one.
Why? Let me ennumerate the differences:
1. Santa Rosa. This is the new motherboard chipset from Intel and the new MBPs are among the first laptops to support them. It has a new, faster memory architecture which allows for faster transfer of data and consequently a faster machine beyond that which is obvious from clockspeeds.
2. The new chipset also allows for a maximum of 4Gb RAM. RAM is also extremely cheap at the moment. I got a couple of 2GB sticks for USD198. Shipping of course is extra. Even without upgrading; the new MBPs come with 2GB base.
3. The LED backlit displays provide for brighter and more importantly more even saturation of colors. Put two MBP displays side by side and the newer LED displays are immediately obvious in clarity. You will however need to tweak the ColorSync profile ( A Gamma of 2.2 is essential). The displays are also supposed to stay brighter for a longer time as opposed to the brightness degradation seen in CCFL displays.
4. WiF "N" aka Airport Extreme enabled out-of-the-box.
5. Larger built in harddrive (I've since upgraded to a Western Digital Scorpio 250Gb internal) with my original drive in a OWC Mercury FW800/400/USB2 external case. Schweeet.
6. Do you really need six reasons?