Can you see the difference with the naked eye whether Venus is at the other side of the Sun or at the Earths' side? When Venus is at an angle with the Sun from the Earth's perspective we are able to see the reflection of the Sun on Venus. But imagine that Venus is on the farthest half of its orbit around the Sun. In that case the planet is further away but we receive his reflection on a larger plane. So could an eye see the difference whether Venus is further away in his orbit or closer to the Earth?
The apparent brightness of Venus does vary.  The distance and phase both affect the brightness, and the light doesn't reflect equally in all directions (though this effect is less significant than in the case of Mercury)

The maximum brightness of Venus occurs at a phase angle of 125 degrees. This is a crescent (0 is full, 90 is half lit and 180 degrees is when Venus transits the sun.)

The brightness curve doesn't vary extremely



In this image generated from NASA data by David Barry you can see the peak brightness is about -4.9.  There is a short central dip. The brightness drops to about -4 as Venus gets further away (even though its phase increases) and note the small rise when Venus is most distant (due to more light being reflected directly than at an angle). These occur when Venus is close to the sun in the sky, and so the brightness can be lost in the dawn or dusk sky.

Judging the difference between -4.9 and -4 is rather difficult, especially as you are not viewing it against a dark background.