One notch more expensive than the LX model, and the main difference is sealed bearing pulleys. The reverse "rapid-rise" low normal action means you move the left and right shifters the same direction for the same result. It's the way to go, unless you have old habits you don't want to unlearn, even though it's easy to do so.

The long-cage model is the default choice. It wraps up to 45 teeth of chain, which allows you to be in the small front ring and any cog in back. The mid-cage model doesn't wrap as much chain, so if you're in the small front ring, you have to be in the larger half of the rear cassette. If this means beans to you and you want the increased ground clearance and slightly reduced weight of the mid-cager, then get it. If not, just get the long-cage model, and it'll be great.

They'll both shift to 36t in back.