The evening service on Good Friday is the Lamentations of Christ or the Matins of Holy Saturday.
The other service is the Unnailing of Christ from the Cross - usually at 3 PM.
This OCA parish doesn't do Lamentations, but has the Unnailing/winding-cloth Vespers at 6. I'll for sure be attending that one either way, for my first time.
Some churches perform the royal hours immediately after the Thursday night Passion (e.g. Matins of Holy Friday) - others perform them on Friday morning.
This parish has both Matins (7:30 am) and 6th/9th Royal Hours (11:00 am) on Friday morning. Which of these two would be more important?
If by Matins you mean what many other parishes read on Thursday night as the Passion Vigil, the service with the 12 Passion Gospel readings, then I would consider this the more important. The Royal Hours basically recap the same readings, except that each Hour focuses on the Passion narrative according to only one of the four Gospels (all four Gospels covered over the course of all the Royal Hours: 1st, 3rd, 6th, and 9th). The Matins of Holy Friday (Vigil if read on Thursday night) covers the whole Passion narrative from the time Judas Iscariot left the Last Supper to commit his act of treason all the way to Christ's death and burial, and from all four Gospels. If you cannot attend both Matins and the Royal Hours, then Matins is the one I would advise you to attend.