Keep in mind that there are two versions of 9 volt batteries. One has 7 cells and the other has 8 cells. If you are using batteries with 8 cells, you need to make sure that your charger will fully charge them.
The Maha charger charges both 7 and 8 cell batteries. I am not sure about the other one.
Another q if you don`t mind.. am I right in thinking that any 9.7v PP3 is going to be an 8 cell battery and so any charger capable of charging 9.7v PP3`s will fully charge an 8 cell PP3?
You are correct, if the charger specification states that it will fully charge a 9.6 volt NiMh 9 volt battery, it will also charge a 7 cell 8.4 volt 9 volt battery.
Will have to wait for the battery to arive so I can check the voltage, then decide whether I need the more expensive maha or the cheaper more feature rich one that may or may not be capable of charging an 8 cell PP3.