just decide on a type of connector that you like and change them all so you can use any of your batteries.
Deans are good, fool proof but fiddly to solder, Corrally type 4mm bullets easy to solder but you can easily connect them up wrong and short out your speed controller.
I use 4mm bullets with red/black coloured heat shrink for easy identification.
http://cgi.ebay.co.uk/4mm-Gold-conne...item4aa4641481
There are other connectors too but avoid the tamiya type as they cannot take the heat generally.