I prefer the Web site on my computer.
Well, I don't have the ability to view Facebook on a mobile device, because my only mobile device is a basic cell phone. (I can only use it to make phone calls, send text messages, and use the calendar, alarm, & 3 games that came on it.)
But, I've seen screenshots of Facebook on other people's cell phones. Based on what I've seen, I still prefer the Web site on my computer.