Below you can see the front view size comparison of Nikon D300 and Sony A7 II. Sony A7 II is clearly the smaller of the two cameras. Its body is 20mm narrower, 18mm shorter and 14mm thinner than Nikon D300.
Nikon D300 vs Sony A7 II - Front View
Nikon D300 vs Sony A7 II - Top View
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.
Camera Size Comparison
Select Two Cameras for Size Comparison