If you're trying to maximize profit, minimize risk, your best "bet" is a single, high-payout gamble, or in other words, Powerball (of course, it would really need to be your lucky day to ensure they were doing a drawing that evening). Although the odds against winning are astronomical, you know you will win, and you winning isn't automatically any more suspicious than anyone else winning.
If you have any pattern of suspicious wins at a casino, they can ban you at will, they don't need a justification. And, at least according to Bringing Down the House, extralegal enforcement is still a Vegas reality. In other words, an overly "lucky" winner might get a visit from a tough guy... or just disappear.
Modern casinos are incredibly sensitive to any threat to profits. They're perfectly happy to ban someone just for being lucky, even if no cheating at all is ever observed. For The advantage, to you, for a lottery, on the other hand, is that it's always expected that someone will win. No one has a vested interest in that money not being paid out.