I have another curiosity question: Why is there a 10-pin AVR ISP connector and a 6-pin version?
It seems that the only difference is that the 10-pin version uses the extra pins for a heap more ground pins.
I personally prefer the 10-pin version because it is much easier to get 10-pin IDC connectors at most electronics stores. I have only seen 6-pin connectors at really specialized online stores like Digikey and Element14. But why is there the need for so many ground connectors?