Good comment. In this example, words are better because (a) they are easier to read, and can be just as precise, and (b) you (specifically) probably aren't going to make as many mistakes with them. On the other hand, if you trying using math notation and find yourself all tangled up, that may be a sign that you don't understand what you thought you meant. This is a major use of mathematical modelling: to show ourselves that what we thought we understood, we don't. It's easier to fool ourselves with words.