Nikon 50mm f/1.8 or 40mm micro f/2.8?

I'm just a casual photo taker, I have a Nikon D3100 and want a new lens. I like to take macro pictures about 1/3 of the time, so the 40mm micro seems like a good choice. But, the 50mm has a bigger f stop for about $100 cheaper. I do about 1/3 portraits, 1/3 macro, and 1/3 misc.family and friends shots. Is the close focusing distance on the macro that much better on the 40mm to where I should spend more for it?

The 50mm lens is not a macro lens. The 40mm lens will do 1:1 macros.

The 50mm f1/8 is 1.3 EV better than the 40mm f/2.8.

So you are trading off a faster lens for a macro lens.

If you desire 1:1 macro, your only choice between the two lenses is the 40mm.

The 40 mm macro lens is a fine one, however it is too short to be used as a portrait lens. If you want to combine your uses, you need to look at the Nikkor 60 mm Mirco f/2.8

You mentioned macro first so I assume you want it more. Get the 40mm. You can also do portraits with it. The 50mm f/1.8 is very cheap. You can grab it later.