Hand held poker games

On a video poker chatroom, I was reading a thread about holding all five cards when you're dealt a 4-of-a-kind. Everyone seemed to know the reason why to do this -- except for me. I asked why, but no one responded. Is it so obvious that everyone was rolling their eyes at me for being so clueless? Sign up for amazing offers & product updates. Under each of these decisions, which yields the highest probability of winning something and which one yields the highest payout? This problem can be solved exactly by using combinatorics, conditional probability and expectation, but since a video poker game is basically a simulator (though likely biased), I wrote my own simulation. For the answer, scroll to the end!

"The cards are chosen at random and the games are fair. There is no switch inside the machine that can make the machine loose or tight. Do not be fooled by Pull tabs which are not real video poker games. What is the worst hand in poker? Now somebody needs to implement the algorithm for the optimal playing strategy as outlined here: http://wizardofodds.com/games/video-poker/strategy/jacks-or-better/9-6/optimal/