It isn't a brand issue.

Basically whether you have a Dell, Apple, HP or Toshiba most processors are made by AMD or Intel and they are placed on motherboards made by other companies but are designed to fit specific processors. The experts all point to Intel as the more powerfull of the 2 AMD versus Intel and that part of the reason Intel is usually more expensive. You need to look at the Intel site and compare model numbers of the i7 and find the one that fits your needs then find our what brand/models have that processor you want. Typically if you buy at a retail outlet you will not see the mainstream Intel i7 models. If you go to the manufacturer sites you will have more flexibility in processor choices. You will be able to select whic processor you want from the ones offered.

Here is a list of all the components in a computer if you by a Dell almost nothing in the Dell is made by Dell and no company either will you find a company that makes all the components in the PC. The advantage Apple has which helps with support is every PC of the same model contains the same components. The Windows machines vendors mic and match components

http://en.wikipedia.org/wiki/List_of_PC_hardware_manufacturers

Morale to the story look at Intel site unde the i7 processors and looks at the differences and find which one meets your needs and then look for a laptop with that processor. The same model Processor in an Apple with perform at the same level as the same processor in Dell. Thats because the Mobo's are designed to match the the processors.