Originally Posted by X Mode

To me, number 1 is for emphasis. You have stronger feelings about something with that statement. Number 1 could be heard as having more emotion attached to it. That's the way it seems to go often. Choices are often made based on emphasis and relative degrees of formality and informality. There are other things I guess, but those seem to come up quite often.

The speaker may or may not be aware that he or she is making these choices. It depends.