infinitive or gerund?

As you can see, in the first sentence the infinitive form and in the second one gerund is used. I want to know what the reason is. Is there any special rule to use these kind of forms?

1-what we want to do is "to make sure" that any money we're spending is, number one, creating jobs, stabilizing the economy

2-what we are concerned about is "making sure" that the money is spent wisely

The infinitive in the first is required by the preceding "want": they want to make sure, etc.

In the second, the gerund is effectively the object of the preposition "about". They are concerned about making sure, etc.