All things being equal - it is not clear that the best poker player has the lower SD... UNLESS he's playing small tourneys (maybe). zgThe intitial question was $400 for 6 hours of play. I would take the poker player hands down due to the deviation of BJ and very small BR.
However, if both players had $10k and one week of play then without question the skilled BJ player will come out on top.
Raise the BR to $250K, and the BJ player will be making more money. The reason why is that at high stakes making money at poker is tougher simply because there are skilled players at those tables, while at the same time as table limits increase BJ games tend to get better and heat is the only problem.
$400 should be enough for a 6 hour duration for the best bj player in the world to make the risk of ruin not so high assuming you're at a $5 table.