A 14" (assuming the specs on both system are the same) will tax the graphics card a lot less than a 15.6" while providing the same quality of blu-ray/gaming (the only difference, is, well, screensize). I think a 15" may be a tad heavier and larger, but probably more durable as well. The 15" would also eat battery quicker.
I'd have to say:
Easier to run on same specs
not very durable
Runs hotter/system runs harder
Of course, this varies from company to company. A ThinkPad, regardless of screen size, is going to be very Durable, while, say, an HP may not be as much.