A chisel plow isn't defined by width or what kind of shovel or point you run on them.  Back when we used to plow, we run 16" sweeps most of the time for working that summerfallow but if the ground got really hard we would use twisted spikes on the first time through.  Chisel plows may look like field cultivators but will have heavier shanks, heavier frame, and most likely bigger spacing between the shanks.  Chisel plows are primary tillage tools while field cultivators are secondary tillage tools.  Go look up a JD 2200 and a 2400 and compare the specs.  Or just look up any field cultivator and chisel plow and compare the specs.  Most companies make both.