There are two differant questions here. Who will win, and who should win.
Who will win? the answer will likely be either soriano, and tejada, both good players, but not having spectacular years. Tejada is the 7th best hitter in the AL adjusting for position, and Soriano is 5th. Soriano is subpar defensively, while Tejada is good. This would bump Tejada up to 3rd on my ballot, and Soriano down to 8th.
This brings me to the real point. Who should win. The answer is really clear: Alex Rodriguez. When you adjust for the fact that he is a SS, he is far and away the best hitter in the AL, and his defense is superb, pushing him into territory no other AL player is near this year ( Kent is though in the NL, and Bonds is otherworldly.) If Soriano and Tejada did what they did with another 50 walks instead of outs, they would be within a few runs of value of A-Rod. Remember its MVP, not MVP for a team that makes the playoffs, and has an offense carried by said player, and the team just makes it in, or participated in a long win streak.