A personal Samsung 16-50 PZ f3.5-5.6 Review plus comparisons

Interestingly the only publication I could find that has tested both (i.e. for consistent methodology) seems to suggest that the S is not really sharper, especially not so in the edges at the wide-end:

S: http://www.pcmag.com/article2/0,2817,2458708,00.asp

At 16mm f/2 the lens betters the 1,800 lines per picture height we used to mark an image as sharp by a wide margin. Its center-weighted score is 2,248 lines, although the edges and corners are a bit fuzzy, showing just 1,529 lines. There' s improvement at f/2.8 (2,498 lines) and f/4 (2,551 lines), but it's not until you narrow the aperture to f/5.6 that the very outer part of the frame sharpens up. The center-weighted score stays about the same at f/5.6 (2,572 lines) and dips a bit due to diffraction at f/8 (2,492 lines), but edges improve to 1,852 and 1,890 lines, respectively.

PZ: http://www.pcmag.com/article2/0,2817,2462581,00.asp

At 16mm it records 2,327 lines per picture height on a center-weighted sharpness test, which is better than the 1,800 lines we use to mark an image as sharp. The outer edges of the image are often a problem area with compact zoom lenses like this, as we've seen with the Sony 16-50mm Retractable Zoom and Olympus M.Zuiko ED 14-42mm f3.5-5.6 EZ. But even at f/3.5 it scores 1,962 lines. There's a moderate improvement in sharpness at f/4 (2,402 lines) and resolution peaks at f/5.6 (2,552 lines).

Notably the 16-50S is tested on the NX30 and the 16-50PZ on the NX3000, but I don't think that should help the PZ much as they have the same sensor resolution.

At the very least with the tested samples the 16-50PZ seems to be the better performer for corner-to-corner sharpness at the wide-end. There is no question that the S is significantly faster at all points in its focal range.