It really depends on what your comfort level is on the street. I quite enjoy the 28-40 FL for street as it gives great depth to your photos adding a nice 3d effect without the compression of the longer lens. The wide angle allows you to get really close and compose without pointing your lens directly at your subject. I find with the longer lens ppl notice more your camera pointed directly at them....With all that said I use the 43 and 77 as well. In places that aren't as populated it is much harder to get close to a subject and the longer lens are helpful.
I am getting the 21 ltd soon but it seems like it would an excellent lens. Don't worry too much about MF on the older lenses as in street using the MF is much quicker than AF (and much quieter
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To start just take our you kit 18-55 and try it out for a couple weeks. See what focal length you use the most and then go from there in getting your lenses....then at least the LBA is backed up with some facts
good luck in your street shooting