I like using an M6 for my putzer and an 8x10 for my driver.
The sharpness of the 180 is almost legendary, but it is limited with respect to close focus. The 120 Makro Planar is better in that respect, and a bit more convenient size-wise, but not quite as sharp as the 180. I overcame the close-focus limitations of the 180 with an extension ring. You might consider that as an option with the 180.