I’d go with whichever one is closer, personally. They both have identical liturgies- The Divine Liturgy of St. John Chrysostom. And they likely have similar small “t” traditions (if I am wrong, my UGCC friends, please correct me!).
In any case just go and absorb. If you can, try and sing along. Keep your head out of the bulletin (I had a hard time doing that- Lutherans never follow something that isn’t in the bulletin

), and focus on what is going on. If you can, stand by someone who is willing to help you throughout. Wear comfy shoes
Other than that, I have no advice for you. Just go and experience- “Christ is in our midst!”