Cameras are comparable in function, features and image quality.
Dimage 7i is closer to digital SLR...imho.
Nikon has edge in zoom. 8x v. 7x.
Dimage 7i has 49mm lens thread. It makes it "relatively"
easy to add lenses.
Dimage 7i is bigger. 5700 is more compact.
It boils down to your personal preferences and what
you hope to achieve with your photography.
Personally, I would lean more towards 7i only because
it is more "D-SLR like" than the 5700.
In the interest of full disclosure, for a short time, I once
owned a 5700 but have not seen or used the 7i.