Are you using floor wedge monitors? If yes how many are where are they positioned?
If you use a single floor monitor right in front of the mic the '104 is the better choice from a gain before feedback stand point (about 7dB to 10dB).
If you use a pair of floor monitors at about the 11 o'clock and 1 o'clock position (looking towards the front of the stage from the mic position) the '105 is a better choice from a gain before feedback standpoint (again about 7dB to 10dB).
If you are using IEM then it won't matter. The '104 is a little bit warmer than the '105.