How comfortable are you being with being up close to the shooting subject? Secondly, how comfortable will be shooting subject be with a big dslr and lens shoved in their face?
Budget?
The 50mm is highly regarded on a crop body as it is 85mm equiv on FF/35mm film. Personally I have the 50 1.4 (after having the 1.8) and if the shooting subject is unknown to me, i find it a bit too up close and personal (since i do a lot of street candids).
If you are somewhat shy like myself, the 85mm 1.8 (1.4 if money isn't a problem) gives you the option of being a little be further away from the subject. Plus, the shoot subject may feel more at ease without a big lens in their face.
I've been using a 70-200 for certain portraits. It really depends on your budget and what other uses you can make out of the selected lens.