You also want your best hitter up as many times as possible, don't you? I sure do. That's the argument for having Betts up first. He's also a pretty damn good leadoff hitter who gets on base and has great speed and baserunning smarts. Also leadoff home runs are not such a bad thing, since teams that take a lead win a high percentage of the time.
All that said, the studies that show that the #2 slot gives the optimum combination of coming up with men on base and coming up as many times as possible.