The vast majority of consumer-grade PCs are almost indistinguishable. The bulk of the components are made by other companies, although Voltmaster does make a good point: Samsung makes RAM, storage (HDD or SSD), and optical drives. They are still buying things like wireless cards, power supplies, displays, and batteries from someone else.
In fact, many PC manufacturers don't even manufacture their own PCs. There are large manufacturing firms, like Asus and Quanta, that build HPs, Dells, Apples, and so on.
In the end I would simply tell you to buy the one with the best features for the price, and to try them out in person. Sometimes there is a deal-breaker like the keyboard.