All my hand planes lie Nielsen, and I have a lot. which is a shame as I'm from the UK, but unfortunately Stanley are not what they used to be. They are very good and well worth the money, if you look after them properly they will be good enough to last a few life times.
If you are going to buy some vintage planes to refurbish take a piece of plate glass with you, lay the plane flat on the glass and try to slide a piece of Paper under each corner, if it slides under any corner just discard it and move on, it will be to much work to try and get the sole flat. It doesn't matter if the base is concave as this will not effect the performance of the plane but the edges must be flat. If it's cheap you could buy it for the hardware.
The low angle jack plane is most commonly for end grain if this wasn't mentioned above.