Sometimes you can customize a ThinkPad so that a T series has the same CPU and RAM as, say, an L series. I guess you can have the same storage and graphics too, but that's not my concern. The question is how are the two customized laptops different in terms of computational power? I think it should have something to do with their motherboards, but I don't know to find those specifications. Is there any information on what makes the designs of these models different?
T-Series is better than the L-Series. The T-Series motherboard uses the QM57 chipset and the L-Series motherboard uses the HM55. In reality this difference is minor if any in terms of performance. The QM57 has more business oriented features and can handle more devices (PCIe, Sata, etc) and the HM55 is really the base version of the chipset line. The real performance difference is the T-Series can be configured with a better CPU in the i7 and the L-Series can only be configured with an i3/i5. If you put the same CPU in both they would perform similarly assuming the graphics and harddrive are also the same.