TypeIt4Me has a chart comparing the features of their software vs. two other popular abbreviation-to-full-word-or-phrase applications, Typinator (which I currently use), and TextExpander.

The main shortcoming on Typinator and TextExpander is that they don’t allow for variable input.

Let’s say I want a phrase that says:
“Hey nnn, thanks for the query. Don’t worry about it, ok nnn?”

… and I want the text expander software to prompt me for nnn, so that I can enter the name of a person and have it appear twice in the phrase.

Typinator and TextExpander only allows you to have the current clipboard content appear at the position(s) you specify, there is no feature that prompts for user input.