Both Sony A77 II and Nikon D3300 have APS-C sized 24.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
One other difference between these two cameras that is worth mentioning is that Nikon D3300's sensor doesn't have an anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the A77 II and D3300 sensor size comparison.
Sensor Size and Resolution Comparison image of Sony A77 II and Nikon D3300 Cameras
Sony A77 II and Nikon D3300 have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture.
DxOMark Sensor Scores
At Camera Decision, we also look at Dxo Mark sensors when available as we think it is a good indicator of image quality.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Sony A77 II
82
24.4 bits
13.4 Evs
1013 ISO
Nikon D3300
82
24.3 bits
12.8 Evs
1385 ISO
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Sony A77 II
or the
Nikon D3300 ,
including hyperfocal distance.
