Come on guys...
First, the X300 is nearly identical to a 9600: both have 4x1 pipes and both are clocked at about the same speed. I don't care about the internals. I wouldn't be surprised if they ARE the same chip, just a newer revision that never saw the light as 9600. You have to take in consideration that, to design a chip, much, much money is needed and is a good idea to reuse anything in existence if possible.
The difference probably doesn't come from the chip itself but the version of the drivers, the amount of software running on the background, etc.
Besides, you are comparing aples to oranges. Thinkpads have always been and will be probably for a long time business machines focused mostly on reliability and durability than anything else. They don't offer wide screen laptops for example. They don't care about puting better video cards unless they are selling "mobile workstations" with the same card but optimized for OpenGL. They put X300 because it's the cheapest discrete chip this days.
About Dells, well, it's easy to explain the Dell situation. They massively produce machines and they try to make them as simple as possible. They almost never (if ever) put flat wires that can break or get lose like Sonys and Compaqs. The keyboard, unlike most other brands, has it's own connector. That makes them VERY reliable and cheap at the same time (they are built at user request and not prebuilt so those measures save money with human mistakes). I am a laptop technician and I haven't seen a single Dell to suddenly die.
Newer Dells have keyboards that are a little filmsy, but previous Dells (like the C610 I used for a while) had very good keyboards, ver like IBM's.
They don't retain value as much as IBMs simply because they are more abundant. There are far (FAR) more spares for Dell laptops than any other brand. It's a simple economic rule that, if a product is abundant, it will invariably go lower in price. But since I have bought all my machines second hand, that's a GOOD thing to me.
Conclussion? I am going to buy a thinkpad. However, I am WELL served with my two Precision M60 (D600 is for sale now).