However, regardless of whether the birchas erusin is a birchas hamitzvos, or birchas hashvach, perhaps it is still fitting for the chosson to hold the ring in order that he has better kavonah during the berachah, and to reduce the time of interruption between the birchas erusin and act of kiddushin, especially as the Rambam holds that it is in fact a birchas hamitzvos.
However, from the Rishonim it is clear that we aren’t so worried about the interruption, if it related to the act of kiddushin, as the Be’er Heitev (Even HaEzer 27 s.k. 1) brings from the Shu”t Maharam Mintz (siman 109, pg. 537): “Immediately, after the birchas erusin without making any interruption, the one who made the berachah should take the ring in his hand, and he should choose two witnesses from the good people of the community, people who are certainly kosher to give testimony ... And he should show the ring to the witnesses so that they see that it is worth a perutah.” The Maharil (pg. 466) writes a similar thing. We see clearly that it is ok to have an interruption between the birchas erusin and the act of kiddushin if it is related.
However, we don’t have clear proof that the chosson wasn’t holding the ring, as it could be that the chosson was holding the ring, and the Maharam Mintz is saying that the mesader kiddushin should then take it out of the hand of the chosson.
