The two GPUs perform quite similarly, though the GT 820M is supposed to be slightly faster. That said, it would be helpful to know the specs of the processors not just their names
E.g: is the i7 a quad core or a dual core? And what generation are they, etc? (generation number is the first number in their name, 5300u = 5th gen).
The likely hood is that the GPU will be more important, but if it's a quad core i7 that could make a big difference depending on what you're doing. Also, what resolution are the two screens? 1080p or something more like 1366x768?