I bet someone (not me) could tell you which would create more loss, a connector or the length of RG58.

Mike,

 

Every connection is a loss.  Some cannot be avoided. Unions using 2 BNC connectors and a male double-ended shaft are electrically ugly.  Long runs of RG 58 are not good.  RG 58 leaks like a sieve, is cheap and doesn't weigh much. 

 

Those answers use very technical terms such as "loss", "not good", "leaks" and "cheap."  "Male" and "shaft" are less technical.  A radio shop person probably knows the losses off the top of his/her head.