Probably the biggest difference in Faith and Buffy in this situation would be that, upon realizing just how powerful the Beast actually was, Buffy would have broken off her attack, gotten away, and planned a better battle strategy, hopefully with some very powerful backup (as in, Spike, Willow, and Xander and his faithful wrecking ball from Season 5.) Faith was always impetuous, always preferring to charge blindly into any situation before assessing the options, and her fight with the Beast perfectly illustrates the fact that she hasn't learned any restraint in prison.