My sister and I both have gaming laptops, hers is a little bit faster (hers has an Intel core i7 9750h whereas mine has an Intel core i5 9300h), there are not many other changes (like mine has a newer BlueTooth version, a 4 cell battery compared to her 3 celled and a larger screen but of the same resolution), still, her battery charger is of 130W while mine is of 135W, why is that so? (Technically, her laptop should require more power)
If i had to reply to you, in summary, options.
Laptops components varies even if from same brand manufacturers, it's a matter of components availabilty and costs.
You have differents cars if you wanna buy one, so different computers you have, i don't see why it isn't logical even more if you both have different brands.