hI,
This discussion seems to be taking an interesting turn. All these circuits will work for current sensing, but these are classified under two catagories, the high side current sensing and the low side current sensing. These two circuits though similar in there approach as they measure the volatge across a fixed resistor to convert the current into voltage by I = V/R. they differ in configration with respect to the position of the current sensing resistor in the circuit loop, low side current sensing is simpler but has its disadvantages as it can't be used in all situations. For more info use google
Asimov