All the tests (of resolution and halftones reproduction) were performed in three modes: 300dpi, 600dpi with disabled toner saving, and 600dpi with enabled toner saving.
The 300dpi printout betrays a considerable loss of detail and shows the familiar artifact. Slanting lines are visibly jagged.
The image is more detailed at 600dpi resolution. The jaggedness of slanting lines is barely visible.
The toner-saving mode is not much different. The image is less saturated and the lines are thinner.
The halftone image printed at 300dpi shows a rude raster pattern, poorly rendered borders between contrasting objects, and low level of detail. Grays are reproduced using a matrix of variable-size equidistant dots. It is hard to read the text at the bottom of the printout.
The 600dpi printout looks much better: sharp contours, better details, a smaller raster pattern, and correctly reproduced light areas.
The toner-saving mode doesn’t bring anything new. The image is less saturated as the toner fill density is reduced.