You want to think twice about the commercial requiring TSA approval? Your first does (unless it's a 61.75, glider or balloon.) The IR does because that gives you a new skill set and the MEL does for the same reason. And all types do. But getting a commercial does not necessarily mean "bigger, faster or heavier." Going from a private SEL to a commercial MEL would, but not because you're getting the commercial, because you're getting the MEL.