<===  The smallest one: A good dictionary for basic word-to-word translation. Easy to carry but very simple. A good tool if you need to quickly look up a common word.

<=== The average one: A good dictionary, though you will not find every word, the entries are more complete than the smaller version.                  
 
<=== The biggest one: The most complete dictionary. Essential if you plan to minor/major in French. Probably too bulky for in-class essays or other settings in which there is a time constraint.