I use the RJ45 method as well. I can correctly terminate an RJ45 end in about 30 seconds, and pinout the RJ45-DB9 adaptor in about another 30. While I am pretty good at soldering, there is no way I could match these times with setting up the iron and all of the other nonsense that goes along with it.

The argument about incorrectly pinned RJ45 adaptors doesn't hold water only because it also holds true for soldered DB9 connectors. A lazy, or uninformed tech can screw either one up equally.