Like with cameras, there is no best one laptop or computer for PP. It's a combination of how much you can afford to spend and what level of performance you want. If you want a high level of performance buy a gaming laptop like an Alienware from Dell. You can select the options you want on their website and the more expensive (processor, memory, SSD, display size, graphics processor) the better the performance you will get. You will also want to buy an external display in the 27" or 32" range, which can be calibrated to srgb. Please note these are big, heavy laptops. Personally, in 2016 I moved from an Alienware laptop to an Apple Macbook Pro, i7 4 core, 2.7Ghz (3.6Ghz turbo), 16GB mem, 512GB SSD, Radeon Pro 455 graphics processor with 2GB DDR5 mem, 15" display. It is thin and light with good battery life, so it's easy to take along to a shoot. I loaded up Creative Cloud including LR and PS and it performs very well.