I've been kicking this around in my head for awhile now and figured I'd toss it out there for public evisceration.
For the record, my gut reaction to the question "Should the Reds be in the AL?" is "Hell no."
The Reds have been in the NL since 1890 and they were one of the eight clubs that formed the core of the NL after the AL came along. The team's entire heritage is wrapped up with the NL and the DH is a sinful practice that deserve rebuking.
And then I asked myself a second question - So what?
They've got books and museums for anyone who cares about the team history. If the AL would be a materially better home for the Reds for the next 30 years, then people in the future can lump the league switch in with other forward thinking Reds moves like night baseball.
I can see two major reasons why the AL might make more sense for the Reds: opponents and ballpark.
Currently we're 14 seasons into the NL Central and the Reds still don't have a rival. Reds fans may not like the Cubs or Cardinals, but those are two one-way streets. Part of that is because the Reds have spent 10 of those seasons posing no danger. Then again, even when they played well and had some tense moments with their most consistent competitor (the Astros), no rivalry emerged from it. The division revolves around the Cubs-Cardinals rivalry and everything else is a secondary storyline.
The AL Central has no such center of gravity. The Indians, Tigers, White Sox and Twins (nee Senators) have plenty of history between them, but there isn't a dominant pairing in the bunch.
Also, if you look at a map, the Reds two most natural geographical rivals are the Indians and Tigers. The annual home-home Battle of Ohio makes for popular baseball, but there's never been anything mutual at stake for both teams. That would change in a major way with the Reds in the same division.
Fans surely could come to dislike the big money team from the south side of Chicago as much as they do the big money team from the north side of Chicago. Plus, the Cubs are a pretty decrepit titan. Beating them is more often a given than an accomplishment. And if you like to tilt at windmills, there'd be 12-14 games a year against the Yankees and Red Sox. Talk about hot tickets.
If the Reds moved to the AL - swapping with either the Royals, Rangers or Tampa Bay - the Pirates could possibly move to the NL East, where they're a much better fit.
And then you get to the biggest reason why the AL might make sense for the Reds, the GAB.
They built it and it will be home for a long time to come. It's a bandbox and it's the sort of place where you could take advantage of a quality DH. Much as the DH disgusts the purist in me, the Reds built a park for DH baseball. Had the Reds been in the AL the past decade it would have vastly improved the return on investment for Ken Griffey Jr. and an AL residence would favorably alter the value proposition for offering Adam Dunn a multi-year extension.
So, acknowledging that it's probably never going to happen and that it would offend my delicate sensibilities if it did, yes the Reds should be in the AL.