Overpriced? Your Opinion

why are the '73s better daily drivers?

Nissan added new improvements all the time. Compared to a '71, a '73 has retractable seatbelts, intermittent wipers, the later style transmissions (eases possible tranny swaps), and improved differential location (better halfshaft angles). Many people who want to keep them stock don't care for '73s because they have the despised emission-carbs here in the USA. But if you are planning to mod the car anyway, just use the earlier style carbs (assuming they haven't already been swapped) and you're golden.