Which lens is better for me?

Nikon 85mm af 1.8f or the nikkor af-s 50mm 1.4f
My preferred type of photography would be protraits… I use a nikon d3100

Your camera will only auto focus with AF-S. Lenses.

Hard choice.

The 85mm is generally preferred for portraiture as the slight telephoto helps compress facial features a bit - which is a bit more flattering.

The 50mm, even though at a 1.5x DX crop factor in your camera is equivalent to 75mm, the lens compression optical character is still 50mm.

The 1.4 is going to allow you to achieve a slightly better DoF, but there's not a lot of difference between 1.4 and 1.8 in this area.

Both lenses have 9 blade aperture diaphragms, so bokeh should be good on both of them.

Of course, AF-S will allow you to focus automatically in your camera, but then again, for portraiture work, it isn't a big deal to focus manually.

So a slight edge for the 85mm in it's optics, and a slight edge for the 50mm for AF-S and f/1.4.

If one lens is significantly less expensive than the other - that might be the deciding factor.