The second option maintains electronic contact with the kit lens. The first one everything is manual including metering.
For the later option, the 50mm lens reversed acts like a multi-element close up dioptre for the kit lens. You can get much more magnification especially when the lens that is fixed to the camera body is of a longer focal length. E.g reversing a 50mm onto a 100mm lens gives u a magnification of X2
Not sure how a reversed lens setup compares to a good achromatic multi element closeup filter, but a reversed lens such as an ( asymmetrical construct ) 50mm should be employed for > 1:1 for better results.