Lewes Court rooms are like swanky hotel rooms with their own bathrooms (you gotta clean it yourself though), East slope is...less like that. Imagine the difference between staying in a Youth Hostel and staying in a 3 star hotel, basically, with everything that accompanies that.
But, as we've decided before, how much you enjoy living on campus is determined almost 100% by the people you live with, and you have no control over that. So basically go for whichever room/house you would most like to live in.
Remember, though, you won't necessarily get Lewes Court. Loads of people put it as their #1 choice.