Tamiya (small or large) or Deans connectors are what they're called and the most popular ones in the Airsoft world (there's also "mini deans" and Traxxas connectors but those are popular in the RC world and split 50/50 about from what I can see). Pretty much because of differing amounts of contact surface more or less amperage can get pushed through the connectors to the wires.
The consensus is that Deans and Traxxas are the best connectors but Deans has a larger "market share" in the airsoft world and as such is probably the one you want to be using.
Secondly the size of the batteries like "mini" or "stick" or "nunchuck" or "brick/large" is the size and configuration of the battery. Ie. if you want to store your battery in a full stock or in a forward PEQ/battery box then get a large pack, if you need it in a MOD stock then a nunchuck is the one you want am I making myself clear?
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE