AER/CAR are the same thing and should be used for comparing deposits. Note that they are generally gross so DIRT of 20% will normally apply. Note also that the AER/CAR on a regular saver account are a little misleading in that because the money is being drip fed you don't get that rate on all lodgements over a single year of saving (e.g. first lodgement is there for 12 months, second for 11 etc.). See my earlier post for more on this.