I have both the 85mm 1.8 HC, and the AF 85mm 1.4, both are really good. The 1.4 is just fabulous at all apertures and is the first choice for portraits with shallow DOF, but would be overkill for your landscape work, both in price and weight.
The 1.8 is much more compact and I agree with the others in that it should be your first choice, and don't dismiss the single coated version, especially if you are shooting B&W.