Billy Beane's Oakland A's.
The Red Sox fielded the best lineup in baseball during the regular season and swung the bats well against Tampa Bay in the ALDS. Jacoby Ellsbury and Shane Victorino fueled Boston's relentless hitting assault on David Price, Matt Moore and co. The Tigers have an elite offense as well, one that led all teams in batting average and finished second only to Boston in runs scored, OBP, slugging, OPS, and total bases. However, much of that production came from likely MVP Miguel Cabrera, whom injuries have reduced to a shadow of his former self for over a month now. Even with a diminished Cabrera, Detroit still features plenty of firepower in Prince Fielder, Austin Jackson, Victor Martinez, Torii Hunter, and Jhonny Peralta, but that lineup becomes a lot less scary when Cabrera can't hit the ball out of the park.
On the mound the Tigers hold the edge, albeit a slight one, and only in the starting rotation where they have three top guns in Justin Verlander, Anibal Sanchez and probable Cy Young winner Max Scherzer. However, this advantage is mitigated by Boston's superiority in the bullpen as well as in the field, where the Tigers are atrocious. The defensively sharp Rays struggled mightily with Fenway Park's monstrous wall and quirky dimensions, so it's not much of a stretch to imagine the Tigers also enduring their share of difficulties.
Furthermore, the Red Sox have two additional advantages to take into account: home field advantage and rest. It's no secret that Boston hits and plays much better at home than they do on the road, and should the series come down to a Game 6 or 7 they'll be thankful to be playing those games at home. As for rest, the Sox haven't played since Tuesday and will hand the ball to Jon Lester (working with a full week's rest) in Game 1. With only one off-day squeezed between their do-or-die fifth game in Oakland and the series opener in Boston, Detroit cannot go with Scherzer or Verlander. Instead, they will counter with Sanchez, the American League ERA leader. It's worth noting (or not, depending on what you think of small sample sizes) that Lester did not pitch well in his two starts against the Tigers this year, surrendering 17 hits in 12 and 2/3 innings. Sanchez did not face the Red Sox this year which should work in his favor, at least the first time through the order.
Lastly, while the importance of managers is often overstated, both teams are in good hands with John Farrell running the Red Sox and Jim Leyland guiding Detroit. Leyland's the superior skipper due to his extra experience, particularly in the postseason.
Taking everything into account, this is going to be a hard-fought, entertaining series. Both teams are well-equipped to win the AL pennant, so picking a victor is essentially a toss-up. I'll say Red Sox in seven.