Note that this comparison is somewhat unfair, as the Dell Inspiron is the "consumer" class machine, while that Dell Latitude is the "business" class machine. The IBM Thinkpad T-series and Z-series are the "business" class machines, while the R-series and A-series are the low-end business class machines. The Lenovo 3000-series is the "consumer" class machine. But, I'm comparing an IBM T-series with the Small Business version of the Dell Inspiron 6400
1: Sturdy case- The T-series is made from some sort of Titanium alloy. It can withstand a lot of abuse. I personally dropped my IBM T30 on the concrete sidewalk! Not just once, but twice. Sure I cracked 2 corners, but it still worked just fine. My wife is still using that machine today (5 years later).
2: Sturdy case part 2- The Dell just seems like a cheaper case. It creaks if you lean on certain areas. It feels like cheap plastic. I've got several scratches in my Dell from putting it into the carrying case. The ibm never had this problem.
3: Best in class warranty plan- Opt for the on-site next day support plan. They come to your house or office and pick up the computer and usually bring it back the next day.
4: "Air Bags" for the Hard Drive- There is a gyroscope built into the computer. When it senses that the computer is being dropped, it parks the hard drive heads to prevent damage to the data.
5: Easily repairable- You can download the entire service manual for the thinkpads and service it yourself after the warranty runs out. (Dell has this as well, but HP charges $$ for it).