Been running the STANT locking gas cap for several years with no issues to report. The small investment of either the locking door or locking cap provides some peace of mind. These locking parts may deter stupid vandalism or at least let you know tampering has occurred.
***My JK came with the non-locking Mopar door and the biggest positive is keeping mud or snow OFF the gas filler neck! Check out the aftermarket doors on ebay, etc