Crank Set Quality Differentiators I work for a bicycle tour operator in Cambodia. We run daily tours on mostly paved roads. I'm looking to purchase new crank sets for ten bikes but I'm having trouble determining if any of the models are worth additional investment. We don't care about weight, just durability. The tour route is essentially flat. We have a tight budget so I don't want to invest additional money if it's not going to pay off over time.

The specific options I'm considering are Shimano FC-M171, FC-M371 and FC-M361 for $17, $30 and $40, respectively. What should I take into consideration when deciding which ones to buy?
Shopping advice and product recommendations are specifically off-topic here.

However, general advice:

Shimano makes products in a deliberate hierarchy of incrementally improving features, weight and quality. The feature you probably want is removable chainrings, so when those wear out you don't have to replace the whole crank.

The FC-M361 is from a higher product line (Acera) than the other two and has that feature (you can see the chainring bolts in pictures online) the other two do not appear to have it.