Although either module can be used for numeric answers, the Numeric Entry module has some features that make it ideal, in most cases, for dealing with numbers.
The Numeric Entry module is able to interpret the value of a number and accept alternate forms. For example, 100 and 1.00x102 are graded equivalently. By contrast, the Short Answer module interprets numbers as strings of characters and will grade 100 as incorrect if 1.00x102 is defined in the Correct tab.
Additionally, in the Numeric Entry module, you can set a tolerance, or a degree of difference accepted as approximately accurate within a problem that allows for rounded numbers to be accepted as correct within a defined range. For example, if you were to ask what 1 divided by 3 is, the correct answer would be a number with infinite decimals, 0.3333... By using the Numeric Entry as an answer space, you can enter 0.33 as the correct answer and set a tolerance that will accept, 0.33, 0.333, 0.33333, and so on.