Which should I get, HP Envy or the MacBook Pro?

I will be going to a U.K. College, (Belfast Metropolitan College) in September to study Computing (Computer Science) and I need a laptop that will store good memory (4GB or higher), I already have a good Toshiba laptop, but lately it can't store my coursework and school work and has been running slow. I need a reliable laptop which will act well and a high graphics laptop. I know that both laptops will contain an Intel Core i3, i5 or i7. I also play alot of online PC gaming and was wondering which of the two would be better to buy for gaming.