Originally Posted by Kevin McLain
3. You have a much higher likelihood (4 outs once vs. 1 out twice) of improving to a hand that can beat the most common big draws (flushes and straights)
As Vempele said, your chance of improving is higher if you draw 2.
That's kinda easy to see. If you draw 1, you have 4 outs to a boat or quads. If you draw 2, well, after you draw the first card, you've either made quads (woohoo!
) or you're back to the same situation as when you draw 1: you have trips and a sidecard. So drawing two gives you that one extra shot at quads, and a very marginally higher chance to improve.