On the two you've posted: too much motion blur going on. Need a faster shutter, enough to get very slight motion blur, not as much as you have here.
First picture is great, I feel like i'm observing a scene, I love the seated womans experession and depth of layers to this image.
2nd one, not so sure about, the direct eye contact makes it look more like a portrait. I don't like this so much when I'm in voyeur mode, as I like my street photography to be.
Contrast is funny as well. The first image has tonality nailed, look at the ethnicities and the textures etc, 2nd one looks burned out.
I used to love shooting B+W on chromagenic film and would use a red or orange filter to help me see without colour. It's more difficult with SLR's because this screws up the bayer and the amount of detail. Better to shoot colour and channel mix the RAW before conversion. I wish there was a way to filter the viewfinder only, I know you can put on RAW+JPEG and the mono conversion, but this is only any use for live view, maybe not a bad thing if you are confident zone focusing, which after a bit of practise is probably the best way for street.