e46 323ci vs 325ci

BMW experts, i would like to know the difference between the 325ci and the 323ci.
I know that the 323ci has more torque but 15hp less than the 325ci, what else is different besides the 325ci having an upgraded exaust, software???

there both 2.5 litres

the 323(M52tu) is 170hp and 181 torque


the 325 is 2.5 litre ( M54) 184 hp and 175 torque