When it comes to laptops, you need to decide what matters you more: mobility or performance. If you don't use your laptop as your main computer, meaning you have a desktop at home, then I suppose mobility would be more important and then I'd look into laptop with smaller screens that weigh less. If it's going to be your only computer, you'll probably get one with a 15' screen and then it can't be that light. Macs are more expensive so if money is tight and you don't really need it for something specific like graphic design, I'd go with a PC.