A curiosity question: Car Performance

I have an '03 TL-S. My mom has a 2000 Nissan Maxima, the base model. My horsepower, engine size, yada yada is more than hers...but when I drive her car, hers seems to have more power than mine. I always use premium gas in mine (hers, regular.) Is there some specification that I'm overlooking that would make hers more powerful than mine, or is there something I need to get checked out on my car? Not that mine FEELS like it's lost power driving it on a regular basis; just that when I drive hers, it seems more powerful than mine. Any ideas?