I'm with Jose on this one... I don't like cutting factory connectors off batteries for two reasons: (1) the factory solder joints are probably better than mine; and (2) the possiblilty of shorting the battery when cutting/soldering connectors (yeah, yeah, I know we're always ultra-careful, but playing with battery leads always has the potential for accidents).

My approach has been to use bullet connectors (3.5mm for <40amps, 4.0 or bigger for >40amps) on the ESC leads, then build a 2" jumper with an XT60, EC3, or Deans (depending on the battery) going to a female bullet on the red wire, and male bullet on the black wire. That way I can switch batteries to different speed controllers without connector problems.