I have a Nikon D3100. Which lens is best for taking indoor portraits?

I'm considering the following two:

- Nikkor 35mm 1.4 AF-S
- Nikkor 50mm 1.8 AF-S

But which would you prefer for taking awesome indoor portraits? The 50mm costs about twice as much as the 35mm.

Actually any lens will work for portraits if you have enough light. I use a Canon 18-200 with my
t1i and I also use two strobes at the sides of my subjects and the results are pretty good.

However, if you don't want extra light, say only window light or perhaps some other source,
either of these will work very well.

Here's an example of what one these can do. This is the Canon 50mm f/1.8. The blinds were closed with no artificial lighting used. Of course the only draw back is that your shutter will be slow so you'll have to have your subjects be very still, no blinking etc. Take a peek.

Both are good lenses. With a 35mm lens, you would have to be fairly close to your subject for portraits. Some get a little uncomfortable with having a camera so close to them. As for price, I'm not sure where you shop at but the 35mm AF-S f/1.4 is a lot more than the 50mm AF-S f/1.8 The 50mm 1.8 takes great photos. I'm sure you would be happy with it. If you do a lot of photography in very low light, the 50mm f/1.4 works great for that. But the 1.4 does cost more than the 1.8.

On your body, the 35 is really about 50 and the 50 about 80, so i would go for the 35mm. Plus it saves some money to go towards other lenses. If you don't mind lack of autofocus you can also consider the 50mm 1.8 AF which could be bought for around $120

You can consider Nikon 35mm f/1.8G AF-S DX Lens for Nikon Digital SLR Cameras

Engineered for Nikon DX-format digital SLRs - Optical formula optimized for use with Nikon DX-format digital SLRs
Aspherical lens element - Minimizes coma and other types of lens aberrations, further improving image integrity
Nikon Super Integrated Coating (SIC) - Enhances light transmission efficiency and offers superior color consistency and reduced flare
Exclusive Nikon Silent Wave Motor (SWM) - Enables fast, accurate and quiet autofocus
Close focusing to one foot for creative perspectives and versatility