As for Zone VI modified versus regular Pentax, I offer the following observation without being able to say if the modified version is worth the extra cash. I just compared measurements at different light intensities reflected off of various colored surfaces, using an analog Pentax and a Zone VI modifed Pentax. Reflective surface colors included a green trash can, green foliage, stainless steel, weatherd wood, beige tile, blue sky, turquoise wall, red cardboard, yellow notepad, etc. Light intensity ranged from dim (EV 3) to bright (EV14). Most often the meters agreed exactly. About 20 percent of the time the readings differed by 1/3 stop. On some pink printed newspaper they differed by 2/3 stop; but on red cardboard they matched exactly.
The digital meter is small and sleek, and you can rotate the EV dial with your index finger without changing your grip. But the analog allows a more secure grip, at least for me. If I were now choosing between the two, I would go for the analog, especially if it were cheaper. I don't know how old the analog model I am using is. I bought it used about ten years ago. It has been used a lot however, and has even taken at least two accidental spills, and still works great.