The 2A is the cheapest adjustable mill, the 2D is easier to adjust so I went for that. I wouldn't get hung up on that though, I haven't adjusted mine since I bought it a couple of years ago, mainly due to the fact I've never bought uncrushed wheat. If you're switching between wheat and barley a lot you may find it the quicker adjustment to be beneficial. Likewise if you want to play around with different settings to see how it affects the crush and whether it makes a difference to your efficiency. I find the factory setting works fine for me.