As Big vs. Bigger

A colleague brought to my attention these two sentences:

• Your house is three times as big as mine.
• Your house is three times bigger than mine.

He asked what the difference was and whether one was incorrect or not. I told him that they were both fine, but that the former has a feeling of competition, while the latter anywhere from an objective to a humble feeling.

This doesn't work though with other similar constructions. When you say, "Your house is as big as mine" you are making your house the reference and indicating that his house may be the same size, but that there is likely something else inferior. So there is a feeling of pride involved now. Yet, when you say, "Your house is bigger than mine" you are making a different statement altogether and it has the same feelings as it did when the comparison was three times the size.