The Pri Megodim (Introduction to Hilchos Berachos, ois 14) writes:ראוי שלא להפסיק בין הברכה לקידושין, ומיד אחר הברכה יקדש ושלא להפסיק בחנם – “It is fitting not to interrupt between the birchas erusin and the act of kiddushin, and immediately after the berachah, one should perform the act of kiddushin and make sure not to interrupt for no reason.” Based on this, according to what we mentioned above from the Mishnah Berurah that one should hold the fruit/mitzvah item in his hand in order to recite the berachah as close to the eating/mitzvah as possible, then there is good reason for the chosson to hold the ring. Even according to the second reason that one should hold the fruit/mitzvah item as it helps him concentrate better, perhaps this also applies by the chosson and the wedding ring, unless we say that the very fact that the chosson is standing under the chuppah is enough of a reminder to help him concentrate and he doesn’t need any additional reminders.
